6/09/2010

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Spring Migration Monitoring: Week 9

Yellow Warbler male

June update

As May came to a close, migration slowed to a trickle. The breeding birds have provided lots of entertainment though. On Wednesday we were inside banding when suddenly we heard the distinctive vit-vit calls of Barn Swallows right outside the lab. We turned around to see a pair hovering in the doorway, no doubt scouting for nest locations!

The Tree Swallows have been kicked out of their nest box, either invaded by a House Wren or predated by a raccoon. They have been busy gathering material around the station to re-build a nest in the nest box next door. Hopefully they will have better luck this time! Native to North America, Cowbirds are considered nest parasites because the females lay their eggs in the nests of other species. Most birds have not evolved to be able to tell the difference between their own eggs and a cowbird egg or nestling, so they will care for them all the same. The Cowbird chicks hatch first and quickly out-compete the real offspring of the host species. As cruel as this seems, the cowbird strategy is incredibly smart. Some Yellow Warblers have evolved a counter-strategy – when they see a cowbird egg in their nest, they build a new nest on top of the old one. Last year a volunteer found a triple-decker!

On June 2 we caught our first youngster of the year: a very scruffy American Robin!

WEEK 9

Species

May-27

May-29

May-30

Jun-01

Jun-02

Jun-03

Eastern Wood Pewee

1

Yellow-bellied Flycatcher

1

3

2

Traill's Flycatcher

8

3

2

3

1

Least Flycatcher

1

1

1

Northern Rough-winged Swallow

4

Gray-cheeked Thrush

4

6

7

1

Swainson's Thrush

9

2

2

1

1

American Robin

1

1

Gray Catbird

1

2

2

1

2

Brown Thrasher

1

1

Yellow Warbler

2

Magnolia Warbler

4

2

1

Blackpoll Warbler

1

1

1

2

American Redstart

1

2

1

Northern Waterthrush

2

1

Mourning Warbler

1

1

Common Yellowthroat

1

1

1

1

Wilson's Warbler

1

2

Song Sparrow

1

1

Lincoln's Sparrow

1

Red-winged Blackbird

1

1

1

3

1

Common Grackle

1

Baltimore Oriole

1

American Goldfinch

3

TOTAL

40

30

19

7

13

12