Thursday, March 25, 2010

Blue Jays

John Trott, the seventh grade teacher who introduced me to birding, claimed that Blue Jays are so beautiful that they would be everyone's favorite birds were they not so common and aggressive. 
Blue Jays in the hand, and perhaps in the field, can be aged by the color of the insides of their upper mandibles.  Birds with white-lined, inner mandibles are young, after hatching year birds have black linings. Thanks to S. R.'s sacrifice of his finger, this Jay's inner mandible color is clearly black, not white.  But by January, most Blue Jays mandible linings have turned black (and this bird was caught on 22 March).  But there is another way to age Blue Jays.
Note the alula feather and the primary coverts in this photo.  (The alula is the first, broad, short wing feather, and the primary coverts overlap the outer flight feathers.) These feathers on this bird are uniformly blueish.  Adult birds have dark bars on these feathers.  This bird, therefore, is a second year bird--this summer will be its first breeding season.

1 comment:

  1. Robyn in particular loves Blue Jays in line with John Trott's suggestion. I think she got over the agression issue very easy since she is the first of four children :).


    I love them partly because of their seed/nut planting behaviors. Somewhat similar to an appreciation of N. Mockingbird, I love that these birds are good at protecting themselves and others by fussing at predators or other interlopers on food and territory.

    Bill Benish (& Robyn Puffenbarger)
    P.S. Thanks Dan!

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