1984 SHORT COMMUNICATIONS 405

SHORT COMMUNICATIONS

Cheek plumage pattern in Colombian Ruddy Duck Oxy ura jam aicensis

JONATHAN ADAMS & EVELYN R. SLAVID

IBIS 126: 405407 Received 16 February 1983

The Colombian subspecies of the Ruddy Duck Oxyura jamaicensis andina is reported to be an intermediate link, in geographical location and plumage, between the Nearctic 0. j . jamaicensis (which winters south to Costa Rica) and the southern Neotropical 0. j . ferruginea (which occurs in southern Colombia from about 5"s to Tierra del Fuego) (Scott 1957, Delacour 1959). An expedition sponsored by the International Council for Bird Preservation (I.C.B.P.) visited the Boyaca altiplano in the eastern cordillera of the Colombian Andes during July and August 1982. At the Lago de Tota (5"30'N, 72"55'W; Fig. 1) there was a breeding population of Ruddy Ducks and the opportunity was taken to observe the intermediate plumage phase males present at this site.

Whereas breeding males of the northern subspecies typically have completely white cheek patches, the Neotropical 0. j . ferruginea usually has completely black cheek patches and was placed originally in a separate species (Peters 1931, Blake 1977). The females of these races are more similar. It became apparent from the detailed analysis of the cheek patches of a number of Ruddy Ducks at Lake Tota that the transition from virtually all-white to principally black cheeks was achieved, not

75% 70'

I ECUADOR r' \

FIGURE 1. A map indicating the location of Boyaca province (shaded area) within Colombia. The black dot gives the approximate location of Lake Tota within the eastern Andean cordillera.

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406 SHORT CORl%IUNICATIONS IRIS 126

FILL ~ t . 2 Standardized representation of cheek plumage of I 1 male Colombian Ruddy Duck obsened d t three localities on Lake Tota, Colombia. 1-5 = northern end of lake, A-C = ha, on west shore, 1-111 = ba? on southeast shore

by random mottling as reported by Delacour (1959) and subsequent authorities (e.g., Johnsgard 1965), but through an underlying pattern.

T h e ducks were not found throughout the lake but were located in a number of distinct breeding groups in suitable bays each quite discrete from the other sites. T h e males in each of three accessible groups were studied with high-powered telescopes a t close range and detailed drawings of the plumage patterns were made on site. A total of 1 1 drake Ruddy Ducks was described in this manner and in Figure 2 the individual patterns have been separated into the appropriate groups for each site.

T h e pattern appears to be based on a triangle of points with its apex at either the top or bottom centre of the cheek; black plumage usually developed between two or more of these points in increasingly dark birds (Fig. 2 ) . T h e patterns on the observed specimens were mirrored on the two cheeks, where both were seen clearly. I t is obvious to suggest that the variation in intermediate plumage phase is subject to some genetic control, since the patterns are more closely related within the breeding sites at Tota but differ between them. Mixing between these groups within the lake must, however, be frequent if not continuous.

Delacour (1959) quoted D r Jose Borrero, of Bogota University in Colombia, as having examined nearly 200 skins of 0 . j . andina without commenting on any pattern to the black mottling. A large collection made down the geographical length o f Colombia should, however, have indicated whether there was any e.iidence for clinical or disjunct transition among these intermediate plumages; this should now be the nest step in any investigation of the subspecific relationships. Delacour (1959) and Cramp & Simmons (1977) refer to the appearance of dark cheek patterns in eclipsed males of 0. j . jamaicensis in North America and England but do not state whether this pattern is other than random. Short (1976) has reported a rare morph of Masked Duck Oxyura dominica from Paraguay which also has a white patch with white speckling on the throat of the male’s otherwise all-dark mask.

J .A. wishes to thank the University o f Newcastle Staff Research Fund for a supporting grant \\ hich enabled him to join the I.C.B.P. expedition to Colombia. We also thank Chris Reid for pointing out the reference to Masked Duck plumage morphs and Gary Clemens for his extensive support at Tota .

1984 SHORT COMMUNICATIONS 407

REFERENCES BLAKE, E. R. 1977. Manual of neotropical birds; volume I: Spheniscidae to Laridae. Chicago: University

CRAMP, S. & SIMMONS, K. E. L. 1977. Handbook of the birds of the Western Palearctic, Vol. I. Oxford:

DELACOUR, J . 1959. The waterfowl of the world; Vol. 111. London: Country Life Ltd. JOHNSGARD, P. A. 1965. Handbook of waterfowl behavior. Ithaca: Cornell University Press. PETERS, J. L. 1931. Checklist of the birds of the world. Cambridge, Mass. Harvard University Press. SCOTT, P. 1957. A coloured key to the wildfowl of the world. The Wildfowl Trust. SHORT, L. L. 1976. Notes on a collection of birds from the Paraguayan chaco. Am. Mus. Novitates

of Chicago Press.

Oxford University Press.

2597: 1-16.

Department of Zoology, University of Newcastle upon Tyne, Newcastle NE1 7RU

Clutch size and breeding success of the Pied Flycatcher Ficedula hypoleuca in natural tree-holes

SVEN G. NILSSON

IBIS 126: 407410 Received 10 March 1983

The breeding biology of hole-nesting birds has exclusively almost been studied using artificial nest sites, i.e., man-made boxes. How does this affect the results obtained? Unfortunately, it is not possible at present to answer this question. Previously, I have reported (Nilsson 1975) on differences in several breeding parameters for tit species Parus nesting in natural tree-holes compared with boxes. Here I report on similar differences for the Pied Flycatcher Ficedula hypoleuca.

STUDY AREA AND METHODS

The breeding of the Pied Flycatcher in boxes and natural nest-sites was studied in deciduous and mixed forests at Stenbrohult, southern Sweden (56”37-38’N, 14”lO-1l’E). Dominating trees were Quercus roburlpetraea, Fagus sylvatica, Betula pubescenslverrucosa and Picea abies. A large majority of the nests studied was situated in forests dominated by Quercus and Fagus. These stands were only lightly managed, and the age of the canopy trees usually was 75-100 years. Management consisted of light thinning of the stands. Fertilizing and spraying with pesticides did not occur. For data on the density of flycatchers, see the discussion.

Wooden nestboxes were tied to tree trunks at a height of about 2 m in plots near to (500-1000 m from) the plots where natural cavities were studied. Boxes were 50- 100 m from each other. For the purpose of this study only data from boxes with a bottom area of at least 87 cm2 are used. In other studies of the Pied Flycatcher, the bottom areas of the nestboxes have been 100-125 cm2 (Kallander 1975, Karlsson & Nilsson 1977, Lundberg et al. 1981). The vegetation in plots with nestboxes was very similar to that in forests where natural nests were studied. Nests situated in forests with a strong dominance of coniferous trees are excluded from this study.

Both nests in boxes and natural sites were usually inspected weekly, but more often near fledging. Natural holes were inspected using a dentists’ mirror fitted with a lamp. A ‘breeding attempt’ is a nest where at least one egg is laid, and a ‘full clutch’ is a clutch where the number of eggs remains the same for at least 48 h, and where the nest has not been abandoned. Data reported here are from 1973 to 1979.

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