Thursday, September 27, 2012

Thursday's Results: A Mimi-"day"

I cannot take credit for the bad pun in the title of this post - that was all Michael! 


We banded 14 new birds and had 1 recapture of 5 species today.  Most of the birds banded today came from the family Mimidae including 7 Gray Catbirds and 2 Northern Mockingbirds.  Because it was a slow day and we had so many catbirds I decided that I would dedicate this post to Gray Catbirds.  Although this is a rather dull looking bird from afar, up close it is quite handsome.    

Gray Catbird

Gray Catbird (note black cap on head)

Gray Catbird (undertail coverts)

Ageing these birds is fairly straight forward but as you will see they can be tricky too.  The first thing banders look at when ageing Gray Catbirds is the greater coverts.  In hatch-year birds, there will usually be a molt limit in the greater coverts between the retained juvenile feathers and the replaced "adult" feathers.  The retained feathers will be a dull gray color with a indistinct rusty edging while the replaced feathers will be dark gray without rusty edging.  In the following example, this bird actually skipped a feather during its first prebasic molt.    

This is a more typical example of a molt limit in catbirds with a few inner greater coverts being replaced during the first prebasic molt and several outer greater coverts being retained. 

This bird replaced all of its greater coverts on its right wing leading one to think that is may be an adult bird.  However, a quick look at the left wing revealed that it was actually a hatch-year bird and it retained the second to last outer greater covert. 


Right wing

Left Wing















3 House Wren

9 Gray Catbird

2 Northern Mockingbird

1 Prairie Warbler

1 Common Yellowthroat



1 Common Yellowthroat



# of Birds Banded:  14

# of Recaptures:  1

# of Species:  5

Effort:  75.2 net-hours

Capture Rate:  19.9 birds/100 net-hours

# of Nets:  16

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