Winter Foraging Habits of Communal

Flocking BirdsJohn Rudolph

Winter Field Ecology, Spring 2010Mountain Research Station, University

of Colorado at Boulder

Species in Flock

Introduction

How do birds that flock together in the winter forage in a group without competing with each other for food?

It goes against common sense that birds would group up to forage in winter when there is less food

Observation Location

My house – Fourmile CanyonPonderosa Pine dominate woodsRiparian – Fourmile Creek, lots of

large cotton woods and willowsFeeder on the 2nd flood porch

Observation Methods

Early morning observation

Record bird’s location of foraging by voice

Feeder time vs. Tree foraging2 minute intervals

WBN and BBC foraging locations

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 1001051101151200

1

2

3

4

Bird Foraging Space

WBNBCC

time (seconds)

Loca

tion

3 – Tree trunk

2 – Tree Branch

1 – Feeder

Observation Results

WBN – even in locations with feeders it still primarily feed on the trees

The WBN rarely ventured off the trunk when foraging

WBN Foraging Patterns

Only foraged large branches near the trunk that had rough bark, similar to the trunk

Special adaptations to walk on trunk

No preference for foraging height in tree

Compare to BC Chickadee

Constantly going back and forth from feeder to twigs on the trees

Caches from the feeder in nooks all over tree, usually where branches split

When foraging on cottonwoods, it stays

on the twigs almost exclusively,

feeding on buds

Forage Niche Separation

WBN & BCC foraging location in unique to that species

Lets birds flock together in winter, but not directly compete for food

I was unable to tell a difference in foraging locations on the treesbetween male and female WBN

Works Cited

On Sex-Specific Foraging Behavior in the White-Breasted Nuthatch Thomas C. Grubb, Jr. Journal of Field Ornithology, Vol. 53, No. 4 (Autumn, 1982), pp. 305-314 http://www.jstor.org/stable/4512753

Cornell Lab of Ornithology http://www.allaboutbirds.org/guide/White-breasted_Nuthatch/id