Sunday, September 20, 2015

50 Shades of Common Yellowthroats


It's amazing what a slight shift in overnight winds can do for moving birds to the coast.  Over the last few days we have experienced fairly strong NE winds during the night.  These winds most likely pushed birds that are migrating along the coast further inland.  Last night, however, the winds were light but had more of a NNW direction.  Winds that have a westerly component to them can move birds to the coast resulting in the increased of numbers of birds that we experienced today.  We banded 88 new birds and had 10 recaptures of 17 different species.

We have been capturing a lot of Common Yellowthroats as of late, but we have only scratched the surface as most have not yer reached us.  Common Yellowthroats are by far the most common bird banded at KIBS with anywhere from 1200-1500 of them banded in a fall.

Hatch-year male Common Yellowthroats are highly variable in the extent of black that they can exhibit in their mask.  The mask on some hatch year males is completely absent while other may have a full mask.  The mask on most hatch-year males, however, is somewhere in between.  The following photo collage shows examples of the variation in the amount of black in the mask of hatch-year male Common Yellowthroats.


All of these are hatch-year male Common Yellowthroats
For comparison, the following two photos are of an after hatch-year (adult) male and a hatch-year, sex unknown (probably female).  Note that the after hatch-year male and the hatch-year male (#9 above) look nearly identical.  The age of both of these birds were confirmed by skull ossification.

After hatch-year male Common Yellowthroat

Hatch-year, sex unknown (probable female) Common Yellowthroat


Despite beautiful weather we had a slow morning at Little Bear today. We banded 25 new individuals and recaptured 2 birds of 9 species. We caught a nice mix of resident and migrant species and saw a slight increase in Gray Catbirds today, with 3 new birds banded. This is a species we expect to see in much larger numbers over the coming weeks. Our highlight birds were a pair of hatch year Black-throated Blue Warblers.

We're expecting a cold front to move through the area on Tuesday of next week, it should bring lots of birds migrating with it and hopefully some new species we haven't seen yet this season.


  Species Captain Sam's Little Bear
New Recaps New Recaps
Downy Woodpecker - 1 - -
White-eyed Vireo 1
2 -
Red-eyed Vireo5 - 2 -
Carolina Wren - 1 - 1
Gray Catbird 4 - 3 -
Brown Thrasher 2
- -
Ovenbird- - 1 -
Northern Waterthrush 2 - - -
Prothonotary Warbler 1 - - -
Common Yellowthroat 58 2 13 -
American Redstart 1 - - -
Magnolia Warbler 1 - - -
Yellow Warbler 1 - - -
Black-throated Blue Warbler 6 - 2 -
Palm Warbler (western) 1 - - -
Prairie Warbler 3 - - -
Northern Cardinal - 1 1 1
Painted Bunting 2 2 1 -

 Banding Stats Captain Sam's Little Bear TOTAL
# Birds Banded 88 25 113
# of Recaptures 9 2 11
# of Species 17 9 18
Effort (net-hours) 131.25 47.5 179.25
Capture Rate (birds/100 net-hours) 73.9 56.8 69.2
Nets 25 10 35