parkweb.vic.gov.auparkweb.vic.gov.au/.../word_doc/0005/692051/BBD-FID … · Web viewMany bird species are known ... there are no available data on the habituation of Blue-billed

Flight initiation distances of Blue-billed Duck in response to non-motorised watercraft at Devilbend Reservoir

K. Stamation, P. Moloney and P. Menkhorst

March 2016

Arthur Rylah Institute for Environmental Research, Department of Environment, Land, Water and Planning

Technical Report Series No. 268

Flight initiation distances of Blue-billed Duck in response to non-motorised watercraft at Devilbend

Reservoir

Kasey Stamation, Paul Moloney and Peter Menkhorst

Arthur Rylah Institute for Environmental Research 123 Brown Street, Heidelberg, Victoria 3084

March 2016

Arthur Rylah Institute for Environmental ResearchDepartment of Environment, Land, Water and Planning

Heidelberg, Victoria

Report produced by: Arthur Rylah Institute for Environmental ResearchDepartment of Environment, Land, Water and PlanningPO Box 137Heidelberg, Victoria 3084Phone (03) 9450 8600Website: www.delwp.vic.gov.au /ari

Citation: Stamation, K., Moloney, P. and Menkhorst, P. (2016). Flight initiation distances of Blue-billed Ducks in response to non-motorised watercraft at Devilbend Reservoir. Arthur Rylah Institute for Environmental Research Technical Report Series No. 268. Department of Environment, Land, Water and Planning, Heidelberg, Victoria.

Front cover photo: Male Blue-billed Duck (photographer: Peter Menkhorst).

© The State of Victoria Department of Environment, Land, Water and Planning 2016

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This is the title (or shortened title)

Contents

Acknowledgements v

Summary 1

Background 1Aims 1Methods 1Key results 1Key recommendations for use of watercraft on Devilbend Reservoir 1

1 Introduction 3

1.1 Background 31.2 Project objective 4

2. Methodology 5

2.1 Field methods 52.1.1 Blue-billed Duck..........................................................................................................................................52.1.2 Other species..............................................................................................................................................5

2.2 Statistical analysis 6

3. Results 7

3.1 General observations of Blue-Billed Duck 73.2 Flight initiation distance 9

3.2.1 Blue-billed Duck..........................................................................................................................................93.2.2 Other species............................................................................................................................................11

4. Discussion 13

4.1 Responses to direct approach by a single kayak 134.2 Management options 144.2 Limitations 174.3 Recommendations 18

References 20

Arthur Rylah Institute for Environmental Research Technical Report No. XXX

iii

Flight initiation distances of Blue-billed Duck

Tables

Table 1. Location of Blue-billed Ducks and maximum group sizes observed from the shoreline and from the

kayak per sampling session at Devilbend Reservoir between 23 July 2015 and 20 November 2015. .8

Table 2. Flight initiation distance (n = 30) and the maximum distance at which Blue-billed Ducks flew

(n = 27) in response to direct continuous approach by a kayak at Devilbend Reservoir between

18 September 2015 and 20 November 2015.....................................................................................10

Table 3. Flight initiation distance (i.e. initial escape distance) and the distance at which birds flew in

response to direct continuous approach by a kayak at Devilbend Reservoir between 18 September

2015 and 20 November 2015............................................................................................................12

Figures

Figure 1: Blue-billed Ducks loafing in the deeper parts of Devilbend Reservoir in June 2015 (photo: Roger

Richards)..............................................................................................................................................4

Figure 2. Map of Devilbend Reservoir, showing the three reservoir sections, the waterbird roosting site

(WRS) and the three locations used for scanning the reservoir with a spotting scope: (1) Fishing

Pontoon (FP); (2) Daangean Point (DP) and (3) Eastern Shoreline (ES)................................................6

Figure 3. Initial locations of Blue-billed Ducks at Devilbend Reservoir observed between 18 September 2015

and 20 November 2015.......................................................................................................................9

Figure 4: Estimated flight initiation distance given initial distance from Blue-billed Ducks............................11

Figure 5. The effects of applying 200 m and 300 m buffers around the initial locations of Blue-billed Duck

groups at Devilbend Reservoir observed between 18 September 2015 and 20 November 2015.....16

Figure 6. Map of Devilbend Reserve showing the proposed boating exclusion zone and the boat

launching/exiting site (LS)..................................................................................................................17

Arthur Rylah Institute for Environmental Research Technical Report No. 268


Acknowledgements

We thank the many Parks Victoria staff involved in this project, including: Louise Bracy, Georgia Kerr and Kevin Yorke for initiating the project, as well as Bill Mallinson and Sam Pollard for coordinating field work support and access to the Devilbend Reservoir. We are especially grateful to Andrew Johnson for his assistance in the field—which included doing all the paddling. Thanks also to Roger Richards (Devilbend Foundation) for providing us with information on his monthly waterbird counts at Devilbend Reservoir. Comments by two reviewers, Phoebe Macak and David Bryant (ARI), improved an earlier version of this report.


v


Summary

BackgroundThe Devilbend Natural Features Reserve (NFR) on the Mornington Peninsula, Victoria, provides valuable habitat for 44 species of waterbird, including the Blue-billed Duck (Oxyura australis), which is listed as Endangered on Victoria’s Advisory List of Threatened Vertebrate Fauna (Department of Sustainability and Environment 2013). Parks Victoria is currently reviewing the management plan for Devilbend, which states that provision for future non-motorised boating (e.g. kayaking and canoeing) will be considered for Devilbend Reservoir following further investigation of potential on-water impacts on the conservation values of the reserve. A key component of the further investigations is assessment of the impacts of non-motorised vessels on the behaviour of waterbirds, particularly the Blue-billed Duck.

AimsThe aim of this project was to determine the flight initiation distance (FID) of the Blue-billed Duck when approached by non-motorised watercraft at Devilbend Reservoir. Data on other waterbird species were also collected opportunistically.

MethodsWe visited Devilbend Reservoir on six occasions between 23 July 2015 and 20 November 2015. We conducted 30 direct continuous approaches to Blue-billed Duck and a total of 36 direct continuous approaches to 12 other waterbird species. All approaches were made in a 4 m long, two-person kayak at a speed of ~1 m/s. The distance at which at least one individual of the focal group showed an obvious escape behaviour (i.e. swimming or flying away) was recorded as the FID. If swimming away was the initial response, we continued to approach the group until at least one bird took flight, and this was recorded as the distance at flight (DAF).

Key results Blue-billed Duck responses to the presence of our kayak were obvious, with the ducks often splitting

into smaller groups, changing direction and moving away from us before taking flight.

The mean ± SD FID (or escape distance) for the Blue-billed Duck was 186 ± 79 m, and the mean distance at which Blue-billed Duck actually flew was 126 ± 66 m. The maximum FID for Blue-billed Ducks was 300 m.

There was a positive correlation between starting distance and flight initiation distance.

Blue-billed Duck group size had no effect on FID or DAF.

FID for other species ranged from 142 m for the Great Cormorant (Phalacrocorax carbo) to 40 m for the Black-winged Stilt (Himantopus himantopus).

Key recommendations for use of watercraft on Devilbend Reservoir1. Establish an exclusion zone within Devilbend Reservoir that is off limits to all watercraft. This would

need to include a sufficient area of quality habitat to provide for the needs of up to several hundred Blue-billed Ducks for the duration of the disturbance.

2. Quantify and map Blue-billed Duck feeding habitat (and potential breeding habitat) to help better inform the appropriate extent and location of the exclusion zone.

3. Limit water access to one designated launching site.


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4. Control the number of boat users permitted on the reservoir at any one time.

5. Review these recommendations following further monitoring of watercraft launch rates, and numbers, behaviour, and distribution of Blue-billed Ducks under the changed conditions.



1 Introduction

1.1 BackgroundThe Devilbend Natural Features Reserve (NFR) is located between Hastings and Mornington on the Mornington Peninsula, 55 km south-east of Melbourne. The reserve is 1005 ha in area and includes two reservoirs, Devilbend Reservoir (the largest inland water body on the Mornington Peninsula, at 240 ha) and Bittern Reservoir (30 ha). The Devilbend NFR provides valuable habitat for 44 species of waterbirds and shorebirds, including 14 international migratory bird species (classified as matters of national environmental significance under the Environment Protection and Biodiversity Conservation Act 1999) and the Blue-billed Duck (Oxyura australis), which is listed as endangered in Victoria (Department of Sustainability and Environment 2013). Bittern Reservoir is shallower than Devilbend Reservoir and is very rarely used by Blue-billed Ducks (R. Richards, Devilbend Foundation, pers. comm.).

Parks Victoria assumed management of the Devilbend NFR in September 2006 and subsequently prepared the Devilbend Natural Features Reserve Management Plan (Parks Victoria 2010). Current public use of the reserve is restricted to the Daangean Point area, which includes a picnic area, walking trails and designated shore-based recreational fishing zones (Parks Victoria 2010). Parks Victoria is currently reviewing the management plan for Devilbend NFR, which states that provision for future non-motorised boating (e.g. kayaking and canoeing) will be considered, following further investigation of potential on-water impacts on the conservation values of the reserve. As part of the review, Parks Victoria requires information on the possible impacts of non-motorised vessels on the behaviour of waterbirds, in particular the Blue-billed Duck.

The Blue-billed Duck is a stiff-tailed duck (Tribe Oxyurinae of the Family Anatidae) and the only Australian representative of six species worldwide in the Genus Oxyura. Stiff-tailed ducks are small (600–1100 g) and highly adapted to an aquatic life, diving to catch aquatic invertebrates, but also stripping seeds and leaves from submerged aquatic plants. They rarely, if ever, come ashore. As would be expected for a diving duck, Blue-billed Ducks are usually found in the deeper parts of Devilbend Reservoir (Richards 2007; see Figure 1).

The Blue-billed Duck is listed as Endangered in the Advisory List of Threatened Vertebrate Fauna in Victoria 2013 (Department of Sustainability and Environment 2013) and is considered an important feature of the Devilbend NFR (Parks Victoria 2010). While there is no evidence of Blue-billed Ducks nesting at the reserve, this cannot be ruled out without more intensive monitoring. Monthly records (beginning in 2005) show that numbers of Blue-billed Duck fluctuate considerably at Devilbend Reservoir, with a peak of 3100 individuals recorded in April 2006 (Richards 2007; Roger Richards, Devilbend Foundation, pers. comm.). This is the second largest aggregation ever recorded Australia-wide and represents about 30% of the estimated population in eastern Australia (10 000 birds) (Garnett et al. 2011), though that estimate is likely to be an underestimate because it was exceeded by a single count at one locality during May 2003 (11 897 Blue-billed Ducks at the Western Treatment Plant near Werribee (Loyn et al. 2014 Table 1). Based on the consistent presence of high numbers of Blue-billed Duck, Devilbend Reservoir was listed as an Important Bird Area by Birdlife Australia, one of only 37 in Victoria) (see http://www.birdata.com.au/iba.vm).


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http://www.birdata.com.au/iba.vm


Figure 1: Blue-billed Ducks loafing in the deeper parts of Devilbend Reservoir in June 2015 (photo: Roger Richards)

Research suggests that waterbirds show behavioural and physiological changes in response to human presence, e.g. disruption to foraging, resting and reproductive behaviours, and reduced time spent alert to predators (e.g. Burger and Gochfeld 1998; Frid and Dill 2002; Steidl and Anthony 2000). Common approaches for the management of human interactions with waterbirds include buffer zones or minimum approach distances, regulating group sizes, and restricting access (spatially and/or temporally) (see Stamation and Loyn 2009 for a review). These are often based on the distance at which a behavioural escape response occurs, commonly referred to as the flight initiation distance (FID). Responses of waterbirds to human approach vary considerably between species and can be influenced by a variety of factors, including (but not limited to) starting distance, direction of approach, stimulus type, flock size, physical characteristics of the species and previous exposure to humans (Burger et al. 2010; Fernández-Juricic et al. 2005; Geist et al. 2005; Glover et al. 2011). Thus, management prescriptions need to be based on site- and species-specific data. There is a clear lack of data available on the FIDs of Australian waterbirds to stimuli other than walkers (Weston et al. 2012). While there are some data on shorebird responses to canoes, very little data exist for waterfowl, and as far as we can ascertain, no information is available for the FID of the Blue-billed Duck (see Weston et al. 2012 for a review). Given the lack of scientific information available, there is a need to test the responses of Blue-billed Duck to on-water stimuli at Devilbend Reservoir to help inform future management of the wetland.

1.2 Project objectiveThe aim of this project was to determine FIDs of the Blue-billed Duck to non-motorised watercraft at Devilbend Reservoir. Other waterbird species were tested opportunistically.



2. Methodology

2.1 Field methods2.1.1 Blue-billed DuckWe visited Devilbend Reservoir on six occasions between 23 July 2015 and 20 November 2015. All observations were made between 0900 and 1700 hours and during low-wind conditions (i.e. <20 km/h). Sampling was conducted during two sampling sessions each day, one in the morning and one in the afternoon, allowing at least one hour between each. During the last four visits, we used a Swarovski HD ATS 80 20–60x spotting scope to scan the reservoir for Blue-billed Ducks prior to launching the kayak. The spotting scope was positioned consecutively at three locations—the fishing pontoon, Daangean Point and the eastern shoreline (see Figure 2)—and the location and number of Blue-billed Ducks were recorded.

All approaches were made in a 4 m long, two-person kayak (Safari H2O, Drifter II). The observer (KS) sat in the front of the kayak, while the person behind paddled. We launched the kayak from Daangean Point and headed towards the parts of the reservoir in which the ducks had previously been seen through the spotting scope. Olympus 8x40 DPS R Binoculars were used to scan for birds while on the water. Once a group of Blue-billed Ducks was seen from the kayak, a direct approach at a speed of ~1 m/s was made. Two approach types were trialled (continuous and stepwise); however, we found that a stepwise approach was not practical for assessing the FID of the Blue-billed Duck at Devilbend Reservoir (discussed further in section 4.2) and so the FID reported here is based on a continuous direct approach. We recorded the initial distance between the kayak and the group of birds when they were first detected from the kayak (i.e. starting distance) as well group size and the general behaviour of the birds prior to approach.

When possible, distances from the kayak to Blue-billed Ducks were measured to ±1 m using a Bushnell Elite 1000 laser range finder and/or Leupold RX-II laser range finder. It often proved difficult to get a distance reading on the Blue-billed Ducks, especially when birds were sitting low in the water at >100 m and the vessel was rocking. In these instances distance was estimated using the distance to a larger object (e.g. reed beds, marker post or trees on the shoreline) as a reference point. All observations were recorded into an Olympus VN-5200PC digital voice recorder with a lapel microphone. In addition, approaches were recorded on a Go-Pro Hero4 camera (on head mount) for later review.

The distance at which at least one individual of the focal group showed an obvious escape behaviour was recorded as the FID. We used swimming away (including changing direction and/or splitting into smaller groups) or flying, as indicators of an escape response. Diving was not considered an escape response because we couldn't be sure that it was purely in response to the approach of the kayak and not a part of normal activity. If swimming away was the initial response, we continued to approach the group until at least one bird flew and recorded this as the distance at flight (DAF). If the initial focal group split into multiple groups, then each subgroup was approached separately (if practical), but the maximum distance at which any one bird (from the original focal group) flew was taken as the DAF for the original focal group.

Once back on shore (i.e. at the end of each sampling session) we re-scanned the reservoir for Blue-billed Ducks using the spotting scope (as described above) and the number and location of the Blue-billed Ducks were recorded.

2.1.2 Other speciesAlthough the focus of the study was the Blue-billed Duck, other species were approached using the continuous approach method described above, when time and opportunity permitted.

During the course of our fieldwork, we observed multiple waterbird species roosting or feeding on the first point south-east of Daangean Point [waterbird roost site (WRS) on Figure 2]. During each sampling session we would paddle past this point to reach the Blue-Billed Ducks, and we passed it again when returning to Daangean point. We noted the distance we were from this point, the species present and the birds’ behaviour as we passed. On 9 November 2015 (sampling session 2), we conducted a direct controlled approach to this point, starting from a distance of 250 m north-east of the point.


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Figure 2. Map of Devilbend Reservoir, showing the three reservoir sections, the waterbird roosting site (WRS) and the three locations used for scanning the reservoir with a spotting scope: (1) Fishing Pontoon (FP); (2) Daangean Point (DP) and (3) Eastern Shoreline (ES)

2.2 Statistical analysisPossible links between FID and either group size or initial starting distance were explored using ordinary linear regression. The global (largest) model constructed was FID affected by group size, initial starting distance, and their interaction. Backwards selection from the global model, and forwards selection from the



null model (FID is unaffected by either group size or initial starting distance) were used to determine the optimal model. Comparisons between nested models were carried out using likelihood ratio tests (Zuur et al. 2007). Similar models and procedures were conducted to assess the DAF. All models were analysed in the statistical program R (R Core Team 2015), with likelihood ratio tests conducted using lrtest from the package lmtest (Zeileis and Hothorn 2002).

3. Results

3.1 General observations of Blue-Billed DuckBlue-billed Ducks were observed at Devilbend Reservoir on five of the six visits, with a daily maximum count ranging from 49 to 160 individuals (see Table 1). At the start of each session, Blue-billed Ducks were generally congregated in a large group on the far-east and south-east section of the reservoir (see Figure 3). Blue-billed Ducks were observed less often west of Daangean Point (3 out of 10 sampling sessions) and were in small numbers (10–12) in this location. The maximum group size recorded from the shoreline (using a spotting scope prior to launching the kayak) was usually larger than the maximum group size observed from the kayak (see Table 1).

Detecting Blue-billed Ducks from the kayak at distances greater than 300 m proved to be difficult, even with binoculars. Two Go Pro clips have been provided to illustrate this (see links below). Both show an approach beginning at ~300 m. Clip 1 ‘Kayak approaching Blue-billed Ducks at Devilbend Reservoir on 18 September 2015’ (https://www.youtube.com/watch?v=wZn7w-lNBm0) shows a group of 20 Blue-billed Ducks taking flight at the 2:20 min mark, 100 m from the kayak. Clip 2 ‘Kayak approaching Blue-billed Ducks at Devilbend Reservoir on 20 October 2015’ (https://www.youtube.com/watch?v=sT9UPWahODc) shows a group of 14 Blue-billed Ducks coming into view at the 2:40 min mark before taking flight at the 3:14 min mark, 80 m from the kayak. The maximum distance that we were able to identify a group of Blue-billed Ducks from the water (using binoculars) was 500 m, but in the majority of approaches it was between 300 and 400 m. The person in the back of the kayak was unable to see the ducks with the naked eye until they were within 100 m (as evident in the two clips mentioned above).


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https://www.youtube.com/watch?v=sT9UPWahODc%20

https://www.youtube.com/watch?v=wZn7w-lNBm0%20


Table 1. Location of Blue-billed Ducks and maximum group sizes observed from the shoreline and from the kayak per sampling session at Devilbend Reservoir between 23 July 2015 and 20 November 2015See Figure 3 for map of locations. *Could not get an accurate count through the spotting scope due to sun glare from the water. #Group observed from kayak rather than on the shore through the spotting scope. Numbers in brackets indicate group size when birds were at more than one location. N/A indicates that data is not available (the spotting scope was not used).

Date SessionMaximum group size Location at the

start of each session

Shoreline Kayak

23/07/2015 2 N/A 0 –

18/09/2015 1 N/A 40 C#

18/09/2015 2 N/A 160 C#

9/10/2015 1 103 48 D

9/10/2015 2 100 37 D

29/10/2015 1 58 14 D

29/10/2015 2 50 50 A (10) & D (50)

9/11/2015 1 53 31 D

9/11/2015 2 53 27 D

20/11/2015 1 32* 49 B (12) & D (32*)

20/11/2015 2 0* 40 B (12) & D (40#)



Figure 3. Initial locations of Blue-billed Ducks at Devilbend Reservoir observed between 18 September 2015 and 20 November 2015

3.2 Flight initiation distance3.2.1 Blue-billed DuckWe performed 30 continuous, direct approaches to Blue-billed Duck groups, the results of which are presented in Table 2. During 16 approaches (53%), the initial escape response of the ducks was to swim


9


away. On 11 of those occasions (36%), swimming away also involved the focal group splitting into smaller subgroups and frequently changing direction. During 13 approaches (43%), the initial observed escape response of the group was to fly away. There was one occasion where some individuals flew at the same time that others swam away. On 13 of the 16 occasions when swimming away was the initial flight response, we were able to continue an approach until one or more ducks flew. The distance at which ducks flew (i.e. DAF) is therefore presented in addition to the FID for 27 approaches (see Table 2). The mean FID distance was 186 ± 79 m and the mean DAF was 126 ± 66 m. The maximum distance at which birds were observed escaping was 300 m. Sixty per cent of approached groups showed an initial escape response at distances of between 200 and 300 m. A total of 83% of approached groups flew once the vessel was ≤200 m away.

Analysis of the FID showed that it was affected by starting distance (P-value = 0.002), explaining some of the variation (adjusted R2 = 26.0%). For every extra metre distant at the start of the approach, the FID increased by 0.45 m [95% confidence interval (CI) 0.18–0.73 m, see Figure 4). This suggests that if a kayak begins its approach at a distance of 300 m from the ducks, the expected FID is ~180 m (95% CI from 154–206 m, see Figure 4). Group size did not influence FID.

The analysis for DAF found that group size and starting distance had no affect. The mean DAF was 126 m (95% CI 100–152 m).

Blue-billed Ducks showed a consistent movement pattern when flying away. If the approach occurred in the east-south-east section of the reservoir (see Figure 2), then the birds would fly west to the central section of the reservoir. If the approach occurred in the central part of the reservoir, then the birds would fly east to the east-south-east section. They would typically fly an estimated 300–500 m before landing.

Scanning the shoreline for Blue-billed Ducks at the end of each sampling session, i.e. after returning to shore (this was done on four of the five visits on which Blue-billed Ducks were observed), revealed that the ducks returned to their original location within 40 min of the end of the sampling session. The only exception to this was on 20 November 2015, when the group of 12 Blue-billed Ducks observed in section B (see Figure 3) at the beginning of both sampling sessions was not there at the end of the second sampling session.

Table 2. Flight initiation distance (n = 30) and the maximum distance at which Blue-billed Ducks flew (n = 27) in response to direct continuous approach by a kayak at Devilbend Reservoir between 18 September 2015 and 20 November 2015

Bird group size and the distance at which the approach started are also presented.

Group size Start distance Flight initiation distance

Distance at flight

Min 1 100 36 27

Max 160 500 300 250

Mean 22.8 315 186.5 126.1

Standard deviation 30.1 93.9 79.2 66.2

25th percentile 5 250 107.5 80

Median 13 300 200 100

75th percentile 30 400 250 190

95th percentile 49.5 500 300 235



Figure 4: Estimated flight initiation distance given initial distance from Blue-billed DucksShaded area is 95% confidence interval. Points are actual data, with colour intensity representing frequency.

3.2.2 Other speciesWe performed 36 continuous, direct approaches towards waterbird species other than the Blue-billed Duck, as the opportunity arose. In total, 12 additional species were approached, with a range of 1–8 approaches per species. The FID and DAF are presented for each species in Table 3. Mean FID ranged from 142 m for Great Cormorant (Phalacrocorax carbo) to 40 m for Black-winged Stilt (Himantopus himantopus).

We observed multiple waterbird species roosting at the waterbird roost site (shown in Figure 2). Species using this area included Australian Pelican (Pelecanus conspicillatus), Australian Shelduck (Tadorna tadornoides), Great Cormorant, Pied Cormorant (Phalacrocorax varius), Little Pied Cormorant (Microcarbo melanoleucos), Little Black Cormorant (Phalacrocorax sulcirostris), Black-winged Stilt, Cape Barren Goose (Cereopsis novaehollandiae), Masked Lapwing (Vanellus miles) and Straw-necked Ibis (Threskiornis spinicollis). Paddling parallel to this point at distances >200 m seemed to have little effect on the birds, with birds continuing with activities such as preening, resting and feeding as we passed. We paddled closer than 200 m on two occasions: once at 120 m (9 November 2015, session 1) and another at 170 m (20 November 2015). We noted that passing at 120 m caused some cormorants to fly and remaining birds to be alert, while passing at 170 m caused some cormorants to fly, but the remaining birds showed no response. During the direct controlled approach to this point (on 9 November 2015), there were 5 Masked Lapwings, 3 Little Black Cormorants, 5 Little Pied Cormorants, 9 Australian Pelicans and 2 Black-winged Stilts on the shoreline, as well as 18 Australian Shelducks in the water (~20 m west of the point). All cormorants flew at 126 m and the remaining birds were alert. All remaining birds took flight (including the shelduck in the water) when the kayak was between 40 and 60 m from the point. The point was checked 40 min later (prior to leaving Devilbend NFR) and only two pelicans and one Little Pied Cormorant had returned to roost.


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Table 3. Flight initiation distance (i.e. initial escape distance) and the distance at which birds flew in response to direct continuous approach by a kayak at Devilbend Reservoir on sampling sessions between 18 September 2015 and 20 November 2015Species Flight initiation distance Distance at flight

Species n Mean SD Min Max 95th percentile n Mean SD Min Max 95th percentile

Australasian Grebea 3 50 0 50 50 50 3 2 50 0 50 50

Australian Pelican 1 60 – – – – 1 – – – – –

Australian Shelduck 3 46.2 21.4 28.5 70 67 3 3 45.3 22.5 26 70

Great Cormorant 3 142 51.9 100 200 192.6 3 3 142 51.9 100 200

Black Swanb 8 102.4 63.3 45 200 200 8 8 74.6 57.0 27 200

Black-winged Stilt 1 40 – – – – 1 1 40 – – –

Eurasian Cootc 7 73.1 42.4 35 160 139 7 6 44.6 9.1 35 60

Little Black Cormorant 1 60 – – – – 1 1 60 – – –

Little Pied Cormorant 3 53.0 12.6 38.4 60.4 60.3 3 3 52.9 12.6 38.4 60.4

Musk Duckd 4 92.5 43.5 50 150 142.5 4 – – – – –

Pacific Black Ducke 1 55 – – – – 1 1 55 – – –

Pied Cormorant 1 92 – – – – 1 92 – – – –aTachybaptus novaehollandiae. bCygnus atratus. cFulica atra. dBiziura lobata. eAnas superciliosa.


13Flight initiation distances of Blue-billed Duck

4. Discussion

4.1 Responses to direct approach by a single kayakThe FIDs presented in this report are the first, as far as we can ascertain, to be reported for Blue-Billed Duck. Blue-billed Duck responses to the presence of our kayak were obvious, with ducks often splitting into smaller groups, changing direction and moving away from us before taking flight. The mean FID (186 m) was a lot higher than the FID of 18.9 m that has been reported (Weston et al. 2012) for Musk Duck (another species from the Tribe Oxyurinae) in response to a walker. Our mean FID for Blue-billed Duck is also higher than that of any other Australian duck species (see Weston et al. 2012 for a list of FIDs for 10 Anatidae species) and higher than the mean FIDs reported for waterfowl species (order Anseriformes) in response to non-motorised craft in the a recently compiled global database of bird flight initiation distances (Livezey et al. 2016). Only one other study (Paton et al. 2000) reported FIDs for Australian duck species to non-motorised boats—most work has been done using a single walker as the stimulus (Weston et al. 2012). The FID for Blue-billed Duck reported here was also higher than that of any other waterbird species at Devilbend Reservoir during our study.

Given the difficulties in observing Blue-billed Ducks from distances of >300–400 m, it is probable that some groups may have begun an escape response before we were able to detect them and likely explains the smaller group sizes observed from the kayak than from the shoreline prior to launching the kayak. Thus, the results reported here for FID and DAF may be underestimates, and our observation of 43% of groups flying as an initial escape response may be an overestimate.

Starting distance is considered an important parameter to include in FID analyses as it explains part of the variation in FID (Blumstein 2003; Blumstein et al. 2003; Weston et al. 2012). We found that FID increased with increase in starting distance, consistent with many other studies (Blumstein 2003; Glover et al. 2011; Guay et al. 2013; Weston et al. 2012). It is widely thought that this correlation is the result of an increase in starting distance leading to an increase in time birds spend monitoring the threat; thus, the birds must have already detected the kayak and considered it a threat when the approach began. Dumont et al. (2012), however, point out that it is almost impossible to measure when the stimulus (in this case the kayak) was detected; hence, this theory is based on uncertainty. They suggest that there is more likely a mathematical explanation to the relationship between starting distance and FID than a biological one.

It is widely reported that waterbirds show short-term behavioural and physiological changes in response to human presence. Disturbance can influence the amount of time birds spend foraging, resting, engaging in activities associated with reproduction, or watching for real predators (e.g. Burger and Gochfeld 1998; Steidl and Anthony 2000; Frid and Dill 2002). Frequent disturbance may also increase energy expenditure through an increase in time spent in flight and other high-energy behaviours. A high level of vigilance may involve a high level of energy expenditure due to physiological stress, such as an increase in cardiac output and hormonal changes (Stiegel 1980; Sapolsky et al. 2000). Longer-term consequences (such as reduced breeding success, lower species richness and lower species diversity) have also been reported in areas of high human disturbance (see Stamation and Loyn 2009 for a review). For Blue-billed Ducks at Devilbend Reservoir, the immediate impact is likely to be a short-term disruption to foraging and time spent resting. Birds were able to recover quickly and returned to their original location within 40 min of the kayak returning to shore, and so it is reasonable to assume that one kayak on the water is not likely to have long-term consequences. However, multiple kayaks at different locations on the reservoir would likely cause a more constant and widespread disturbance, which may have far greater impacts.

The strong response of Blue-billed Ducks to a single kayak at Devilbend Reservoir may result from a history of only low-level exposure to humans and watercraft—prior to 2006 there was no public access to the reservoir, and public access since 2006 has been limited to walking tracks in the Daangean Point area. Many studies have shown a correlation between the severity of response and the degree to which the birds have been previously exposed to the stimulus (Ikuta and Blumstein 2003; see review by Stamation and Loyn 2009; Steven et al. 2011). Many bird species are known to partially habituate to human presence through



repetitive and predictable visitation by people (Walker et al. 2005; Walker et al. 2006). The duration and frequency of disturbance that results in partial habituation to people varies widely among species. For some species, partial habituation may occur quite quickly (Walker et al. 2005), but for other species habituation may not occur at all, despite frequent, relatively harmless human visitation (Burger 1981). Many authors have speculated that the observed inter- and intraspecific variation in tolerance to humans in their studies is a result of repeated exposure to humans. For example, Rodgers and Smith (1995) found that Brown Pelicans Pelecanus occidentalis and Cattle Egrets Bubulcus ibis were relatively tolerant of human disturbance compared with other waterbirds in the area. They suggested that this tolerance may be due to the long association with and habituation to human activities by these two species: pelicans frequently associate with fishing activities and Cattle Egrets often follow farm machinery. Rodgers and Schwikert (2002), in their study of the response of foraging and loafing birds in Florida to the approach of jet skis and outboard-powered motor vessels, found migrant waterbirds to be more sensitive to disturbance than resident waterbirds. Thus, it is plausible that the Blue-billed Duck at Devilbend Reservoir may become more tolerant of non-motorised watercraft; however, there are no available data on the habituation of Blue-billed Ducks to support that prediction. Regular monitoring and repeat surveys are an important tool for detecting any long-term changes in Blue-billed Duck responses to watercraft with increasing exposure to that stimulus at Devilbend Reservoir.

4.2 Management optionsFIDs are used to provide a baseline against which to assess management strategies such as set-back distances. The precautionary principle suggests using an upper limit such as the 95th percentile or the maximum distance at which a response was observed, and these upper limits are what is widely used when making management recommendations (Weston et al. 2012). Thus, based on the FIDs reported here, a buffer distance of 300 m would be the most appropriate at Devilbend Reservoir. If a buffer distance of 200 m was adopted, we would expect Blue-billed Ducks to show an escape response in 40% of approaches, and that they would fly in 23% of cases, whereas if the minimum approach distance was set at 300 m, it is likely that Blue-billed Ducks would show an escape response in 5% of cases.

There are a number of reasons, however, why setting a minimum approach distance to Blue-billed Duck at Devilbend Reservoir is not a practical option. The boat user needs to be able to identify Blue-billed Ducks from the minimum approach distance (at least). It is very difficult to see Blue-billed Ducks from a kayak, with the naked eye, at distances >100 m. This would make it almost impossible for recreational users to comply with the approach limit and would be very difficult for managers to enforce. Further, having a 300 m zone from all Blue-billed Ducks could potentially exclude watercraft from the majority of the reservoir. For instance, if we were to use the Blue-billed Duck locations shown in Figure 3 as an example of where ducks might be located on any given day, and apply a 200–300 m buffer, much of the reservoir would become off-limits (see Figure 5). Once birds started moving around in response to the kayak, this zone could potentially get larger and complicate things further.

Given that Blue-billed Ducks show strong responses to watercraft at great distances, allowing non-motorised watercraft across the entire reservoir would likely significantly reduce the amount of usable habitat and consequently degrade this important site for the species. We suggest that a more appropriate management strategy would be to set an exclusion zone that is off-limits to all watercraft. This would provide a refuge area for the ducks, i.e. an area for them to retreat to if they were to be approached by a vessel. Providing an exclusion zone, rather than setting minimum approach distances, will ensure that there is always space available to Blue-billed Ducks for feeding and resting. We suggest a staged approach to opening up Devilbend Reservoir to non-motorised watercraft, starting with a small area where boating is permitted (e.g. anything west of a direct line from Daangean Point to the opposite shoreline, Figure 6), which could be reviewed following monitoring of the numbers and behaviour of both vessels and birds. We assume that the habitat provided across the deeper parts of the reservoir is fairly uniform and that the central and east-south-east sections of the reservoir would provide sufficient feeding habitat if the western section was opened to boating. However, it would be advisable to quantify and map Blue-billed Duck feeding habitat to better inform the appropriate extent of the exclusion zone, especially given that Blue-



billed Ducks have been reported to often use the western section and central section of the lagoon (Roger Richards, Devilbend Foundation, pers. comm.).

We recommend having one launching and landing site for non-motorised boats to limit widespread disturbance. We suggest that the launching site should be near the fishing pontoon, because this site would involve least disturbance to birds in most parts of the central and east-south-east sections of the reservoir. Having one launching and landing site will also ensure that visitors are behaving in a predictable manner, which may assist with habituation of birds within the boating zone. In addition, these areas are currently open to pedestrian traffic and shoreline fishing, and so it is sensible to use these areas and maintain the western parts of the shoreline as non-disturbed sections of the reservoir.

Our observations also indicate that the first point south-east of Daangean Point (WRS on Figure 2) is an important roosting site for many waterbirds at Devilbend Reservoir; if non-motorised boating were to occur in this area, an exclusion zone of at least 200 m around this point would be advisable.



Figure 5. The effects of applying 200 m and 300 m buffers around the initial locations of Blue-billed Duck groups at Devilbend Reservoir observed between 18 September 2015 and 20 November 2015



Figure 6. Map of Devilbend Reserve showing the proposed boating exclusion zone and the boat launching/exiting site (LS)

4.2 LimitationsBecause the Blue-billed Duck is a small bird that sits low in the water, it proved difficult to see from the kayak at distances >300 m, even when using high-quality binoculars. This made detecting an alert response impossible, limited our starting distance to ≤400 m in 90% of tests, and cast some doubt over the true FID. It is probable that the birds may have already responded to us by swimming away and/or breaking into smaller groups before we could see them. Thus, we can’t be sure whether the responses we observed were



truly initial escape responses or actually secondary responses; thus, the FID reported here may be an underestimate.

Efforts were made to reduce the likelihood of testing the same group more than once in a sampling session by trying to keep track of where the birds had flown to and avoiding re-approaching that group. However, as the birds often split into smaller groups and moved around the reservoir while we were on the water, we cannot be entirely confident that there were not occasions when the same birds were resampled during a session. This possible pseudo-replication was reduced by only using the FID of the original focal group and the DAF of ‘subgroups’ combined, rather than treating them as separate approaches.

We trialled a stepwise approach to Blue-billed Ducks on three occasions because it was thought that this approach would best mimic a recreational fisherman’s behaviour (we understand that if kayaking is authorised on Devilbend Reservoir, it will be mostly confined to recreational fishers; Louise Bracy, Parks Victoria, pers. comm.). The stepwise approach involved paddling for 10 m, then keeping the kayak stationary for 5 min before travelling another 10 m. Each time we started our approach, however, the birds were already moving away from us, and they continued to swim away while we sat for 5 min, often moving out of view. While each approach seemed to elicit an immediate flight response, we were not able to get close enough to the group to cause the birds to actually fly. We decided that a continuous approach was the most practical to use in this study in order to report on Blue-billed Duck FIDs and DAF. A slow continuous approach is the most widely used method for assessing FIDs and is the protocol recommended by Weston et al. (2012) in their review of FIDs and their application to the management of Australian birds.

Another technique for measuring flight response, individual focal follows (in which a focal bird is selected from the group and the response of that individual is recorded), was not practical because it was difficult to keep track of an individual Blue-billed Duck in a group, especially when swimming speeds and directions changed frequently. We took the FID (and DAF) as the distance at which the first duck responded. Generally, all members of the group responded simultaneously and used the same escape response; however, on one occasion the initial response of some members of the group was to swim, while for others it was to fly.

Project funding limited the number of survey days as well as the number of stimuli we could test. As a result we were only able to test responses to a single kayak on a small number of days. It is possible that seasonality and the number and type of kayaks on the water could influence FIDs, but testing these variables was beyond the scope of this project.

4.3 Recommendations Set a boating exclusion zone [e.g. east of a direct line from Daangean Point to the opposite shoreline

(see Figure 6)]. The size would need to include a sufficient area of quality habitat to provide for the needs of up to several hundred Blue-billed Ducks for the duration of the disturbance. The size of this zone should be reviewed following continued monitoring of visitation, Blue-billed Duck numbers and behaviour of birds in the presence of non-motorised watercraft, and following identification of key habitat areas. A line of marker buoys could be used to indicate the limit of the boating zone, as is done at Karkarook Lake, Oakleigh South.

Quantify and map Blue-billed Duck feeding habitat, as well as potential breeding habitat, to determine the appropriate extent of the exclusion zone. The observations of Blue-billed Duck locations in this study (i.e. primarily in the east-south-east section) should not be considered as evidence that this is their primary habitat; rather, these observations indicate where they were located at the time of the study. This is important to consider, given that Blue-billed Ducks have been reported to often use the western and central parts of the lagoon as well (Roger Richards, Devilbend Foundation, pers. comm.).

Limit the launching of vessels to one designated area. This would ensure visitors enter and exit the water in a predictable manner. The launching site would be best positioned near the fishing pontoon so as to limit the level of disturbance to the birds in the central and east-south-east sections of the reservoir.



Limit water access to approved groups/individuals initially. This could be reviewed following monitoring of Blue-billed Duck numbers and behaviour.

Continue to support monthly monitoring of Blue-billed Duck numbers and habitat use on Devilbend Reservoir.

From the shoreline, monitor the behaviour of Blue-billed Ducks in the presence of vessels—especially movement patterns and habitat use.

Repeat the direct experimental approaches used in this study (e.g. 1 year later) to compare and identify any behavioural changes e.g. habituation or sensitisation to the presence of non-motorised watercraft.

If boating is to be authorised beyond the west section of the reservoir, ensure that an exclusion zone of at least 200 m is set around the water bird roosting site (Figure 6)



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parkweb.vic.gov.auparkweb.vic.gov.au/.../word_doc/0005/692051/BBD-FID … · Web viewMany bird species are known ... there are no available data on the habituation of Blue-billed