McGILL BIRD OBSERVATORY

SONG SPARROW MOLT

In 2006 we began noticing a rather unusual molt in hatch-year Song Sparrows.  After careful documentation over two fall migration monitoring seasons, we submitted a paper describing what we termed the 'eccentric plus primary coverts' molt to North American Bird Bander.  As a complement to that article, we present below some colour photographs illustrating this molt pattern, as observed at McGill Bird Observatory, in Montreal, Quebec.

 
This Song Sparrow was banded in early August 2006 and was distinctly in juvenile plumage at the time.  Upon recapture on August 25, it was seen to be replacing its primary coverts sequentially, along with the corresponding primaries.  Such a pattern of feather replacement was believed to occur only during second and subsequent prebasic moults, but as this bird has shown, there is still a lot to be learned about even the most common species.  (Photo by Seabrooke Leckie)


The photos above and below show the left and right wings of the same individual captured in August 2007. This individual shows a symmetrical 'eccentric plus primary covert' wing molt.  Note the difference in length of the growing primaries and corresponding primary coverts in both wings, highlighting the occurrence of this molt and making it easy to spot.  (Photos by Barbara Frei)


Note the sheathed feathers coming in, both the longer primaries and shorter corresponding primary coverts.  (Photo by Seabrooke Leckie, August 2006)


Again note the sheathed feathers (both primaries and corresponding primary coverts) coming in, this time longer and easier to see and differentiate. (Photo by Seabrooke Leckie, September 2006)


A close-up of the tiny sheathed primary coverts being grown in over their corresponding primary coverts in a hatch-year Song Sparrow.  (Photo by Seabrooke Leckie, September 2006)


A selection of Quebec region hatch-year birds at the Canadian Museum of Nature.  (Photo by Marie-Anne Hudson)


A selection of Ontario region hatch-year birds at the Canadian Museum of Nature.  (Photo by Marie-Anne Hudson)


The one example found of a hatch-year Song Sparrow showing the 'eccentric plus primary covert' molt described in our submitted paper.  It is likely that there were more in the collection, however determining whether this unusual molt has occurred on a closed wing is very difficult.  We decided to be very conservative and only use birds actively molting to document this molt's historical occurrence in our region.  (Photo by Marie-Anne Hudson)

 

2002- The Migration Research Foundation Inc.