McGILL BIRD OBSERVATORY

 Seasonal status at MBO:

Ageing and sexing guidelines:

January - June:

ASY - U Crown solid black, wing uniformly gray, primary coverts broad, undertail coverts uniformly rufous.  Sexes indistinguishable by plumage. SY - U Similar to ASY, but primary coverts tapered and abraded, and occasionally with some gray feathers on the crown.  Some also retain gray feathers among the undertail coverts, and a moult limit may be visible among the greater coverts.

June - December:

AHY - U Similar to ASY - U (see above) HY - U Similar to SY - M (see above) JUV - U The key characteristics of juveniles are the loosely textured and primarily gray undertail coverts, and the incomplete black cap.

Ageing of Gray Catbirds can require careful examination.  The incomplete black cap on the bird in the photo below indicates it to be SY, but some birds at this age already have a full cap.  During the breeding season, approximately mid-May to late July at MBO, CP/BP can be used to identify sex.

Photo by Marcel Gahbauer, McGill Bird Observatory, May 2005

In theory, the condition of the primary coverts can serve to distinguish between SY and ASY Gray Catbirds.  In practice, however, the distinction is much more subtle than in many other species, and only rarely is the wing enough to determine the age of an individual.  While the primary coverts in the photo below are not particularly narrow or abraded as would be expected, they do conform to SY expectations by featuring only very narrow and indistinct grayish edging.  In some individuals, a contrast between brownish unreplaced outer greater coverts and slate gray replaced inner coverts is visible.

Photo by Marcel Gahbauer, McGill Bird Observatory, May 2005
 

The tail, or more specifically the undertail coverts, can represent a shortcut to ageing Gray Catbirds.  While most individuals replace all their undertail coverts in their first prebasic molt, some such as the individual below do not, and this serves to indicate that it is a second-year bird.  The outer rectrices also tend to be relatively more abraded and tapered than on ASY individuals, a characteristic which may be helpful for the many SY catbirds that do not have any gray among the undertail coverts.

Photo by Marcel Gahbauer, McGill Bird Observatory, May 2005

RETURN TO AGE/SEX OVERVIEW

Note the solid black cap and maroon iris.  A black mouth lining is also characteristic of AHY Gray Catbirds.

Photo by Marcel Gahbauer, McGill Bird Observatory, September 2005
 

AHY Gray Catbirds have uniformly gray wings, but molt limits on HY birds can be faint, and therefore ageing should not be based solely on wing for this species.

Photo by Marcel Gahbauer, McGill Bird Observatory, September 2005
 

The rectrices of AHY catbirds are generally broad and rounded.

Photo by Marcel Gahbauer, McGill Bird Observatory, September 2005

RETURN TO AGE/SEX OVERVIEW

In fall, two of the best field marks for ageing Gray Catbirds are ones which are not easily shown in photos.  HY birds have a grayish-brown to reddish-brown iris, visibly different in most light from the maroon iris of AHY birds.  Also, the mouth lining ranges from white or pale gray to pinkish, unlike the black which characterizes AHY.  The more readily visible features tend to be somewhat variable.  The incomplete black cap on the bird in the photo below indicates it to be HY, but some birds at this age already have a full cap. 

Photo by Marie-Anne Hudson, McGill Bird Observatory, August 2007

Photo by Seabrooke Leckie, McGill Bird Observatory, August 2006
 

The condition of the primary coverts can serve to distinguish between HY and AHY Gray Catbirds, as can the presence of a moult limit among the greater coverts in HY birds.  As the three photos below illustrate, the position of this limit, and the degree of contrast between the old and new feathers can be quite variable.

Photo by Marie-Anne Hudson, McGill Bird Observatory, August 2007

Photo by Marie-Anne Hudson, McGill Bird Observatory, August 2007

Photo by Seabrooke Leckie, McGill Bird Observatory, September 2006
 

Note the loosely textured undertail coverts.

Photo by Marie-Anne Hudson, McGill Bird Observatory, August 2007

Photo by Seabrooke Leckie, McGill Bird Observatory, August 2006

RETURN TO AGE/SEX OVERVIEW

Juvenile Gray Catbirds are overall gray, with some faint barring on the breast.  The crown may begin to have some black feathers.  This general appearance, in combination with the undertail coverts, allows juveniles to be reliably identified.

Photo by Marcel Gahbauer, McGill Bird Observatory, July 2005
 

The wings of juvenile Gray Catbirds are generally uniform in colour, and are not particularly informative for ageing the bird .   

Photo by Marcel Gahbauer, McGill Bird Observatory, July 2005
 

Juvenile Gray Catbirds are easily recognizable by their loosely textured undertail coverts, which are primarily gray, with usually only a bit of rufous showing.

Photo by Marcel Gahbauer, McGill Bird Observatory, July 2005

RETURN TO AGE/SEX OVERVIEW

© 2002-2008 The Migration Research Foundation Inc.