McGILL BIRD OBSERVATORY

PHOTO LIBRARY

American Tree Sparrow / Bruant hudsonien (Spizella arborea)

 NOTE: This species account has been moved to Piranga to allow for improved comparison among examples.  
The updated profile is located at:  http://www.natureinstruct.org/piranga/view.php/Canada/2A86F9C93636CDA3

 Introductory notes:
American Tree Sparrow is one of the more difficult species to age, and determination of sex is generally limited to brood patch / cloacal protuberance during the breeding season.  While molt limits and rectrix shape can be used for ageing, both can be subtle, and many intermediates (especially in spring) may not be safely aged.


QUICK TIPS:
1) Look at the tail - uniformly narrow and pointed rectrices OR contrastingly fresh and broad central rectrices are indicative of HY/SY, while uniformly broad and more rounded rectrices are typical of AHY/ASY

2) Check the wing for molt limits - HY/SY birds show a contrast between darker/fresher greater coverts and tertials vs. the paler block of primary coverts, primaries, and secondaries; on AHY/ASY birds the wing is more uniform in colour and wear

Species account updated January 2011

Ageing and sexing guidelines:

January - July:

ASY - U
Wing relatively uniform in colour and wear; rectrices broad and fairly truncate 
     
SY - U
Molt limit between the replaced greater coverts and tertials and a paler brown block comprising the primary coverts, primaries, and secondaries; outer rectrices relatively narrow and tapered
     

-

July - December:

AHY - U
Wing relatively uniform in colour and wear; rectrices broad and fairly truncate 
HY - U
Molt limit between the replaced greater coverts and tertials and a paler brown block comprising the primary coverts, primaries, and secondaries; outer rectrices relatively narrow and tapered
 

Ageing and sexing details:

JAN - JUL:  after-second-year unknown

 


 


RETURN TO AGE/SEX OVERVIEW

 

JAN - JUL:  second-year unknown

 


 


 RETURN TO AGE/SEX OVERVIEW

 

JUL - DEC:  after-hatch-year unknown

Body plumage provides no useful information about age or sex, and molt limits are only occasionally obvious enough to be recognized on HY birds, therefore it is unwise to call any AHY based just on overall appearance.


Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2009
 


On AHY birds, the wing is dark and relatively uniform in condition (the greater coverts almost always appear distinctly darker).  The primary coverts tend to be broader and more rounded than on HY birds, but this can be a subtle distinction.


A typical AHY wing.
Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2009


A slightly paler wing, but still showing a fairly uniform appearance.  The primary coverts in
this example are particularly broad and rounded.

Photo by Marcel Gahbauer, McGill Bird Observatory (QC),
December 2006
 


The outer rectrices tend to be quite broad and rounded.


A fairly typical AHY tail.
Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2009


A slightly paler tail (corresponding to the paler wing in the previous section).  Although the
central rectrices on this bird are a bit narrower, the outer rectrices are again broad and rounded.

Photo by Marcel Gahbauer,
McGill Bird Observatory (QC), December 2006

RETURN TO AGE/SEX OVERVIEW

JUL - DEC:  hatch-year unknown

Occasionally molt limits can be seen on perched HY birds, but in most cases overall body plumage provides no useful clues to age.  On average, HY birds may be slightly duller than AHY birds, but there is too much overlap for this criterion to be useful except in extreme cases.


Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2005


Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2009


On HY birds, the dark greater coverts and tertials contrast more sharply with the paler brown block of retained juvenile primary coverts, primaries, and secondaries.  The primary coverts and outer primaries also tend to be somewhat narrower and more pointed than on AHY birds.


A typical HY wing, showing the contrast between the two blocks of feathers on the wing.
Note that there is a bit of brownish edging to the primary coverts on both HY and AHY
birds, and this is therefore not a particularly reliable trait to consider.

Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2009

 


Rectrices are typically somewhat narrower and more pointed than on AHY birds, though the distinction can be somewhat subtle.  In this species tail wear tends to be less evident than in many other sparrows, so many HY/SY individuals have relatively fresh looking rectrices.


A typical HY tail, with the outer rectrices distinctly narrower and more tapered than
would be the norm for AHY birds.

Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2009


A slightly paler example, with outer rectrices not quite as pointed at the tip.
Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2009


An example with even more rounded tips to the rectrices; this is sufficiently intermediate
to be inconclusive, and a distinct molt limit would be required to determine age as HY.

Photo by Marcel Gahbauer, McGill Bird Observatory (QC), October 2005

RETURN TO AGE/SEX OVERVIEW 

 

2002- The Migration Research Foundation Inc.