BIRDS OF COSTA RICA

PHOTO LIBRARY

Swainson's Thrush / Zorzal de Swainson (Catharus ustulatus)

 

QUICK TIPS:
1) Look at the greater coverts - the presence of buffy-white shaft streaks indicates a HY/SY bird, however the absence of buffy-white shaft streaks is NOT an entirely reliable indicator of AHY/ASY, as some HY/SY birds may lack these markings

2) Examine the outermost primary (p10) - on HY/SY birds it is rounded and 1 mm longer to 6 mm shorter than the primary coverts, while on AHY/ASY birds it is narrow, pointed, and 4-9 mm shorter than the primary coverts

3) Look at the shape of the rectrices - they are tapered and relatively abraded on HY/SY birds, but rounded and relatively fresh on AHY/ASY birds

Species account updated March 2009

Click here for additional photos of this species in the McGill Bird Observatory ID Photo Library

Ageing and sexing overview:

Spring:

ASY - U
Broad and rounded rectrices; outermost primary (p10) narrow and pointed.

SY - U
Pale shaft streaks on outer greater coverts; rectrices narrow, tapered, and relatively worn; p10 broad and rounded

Ageing and sexing details:

SPRING:  ASY-U (after-second-year, sex unknown)

Overall appearance is of no help in identifying age of Swainson's Thrushes, and there are no plumage differences between sexes.


Photo by Marcel Gahbauer, Las Caletas (CR), April 2008
 


The greater coverts lack prominent pale tips or shaft streaks, but to confirm age as ASY, p10 should be confirmed as relatively short, narrow, and pointed, as in the second photo below.


Photo by Marcel Gahbauer, Las Caletas (CR), April 2008


Photo by Marcel Gahbauer, Las Caletas (CR), April 2008


The rectrices are broad and fairly rounded at the tip, generally in fair to good condition.


Photo by Marcel Gahbauer, Las Caletas (CR), April 2008

RETURN TO AGE/SEX OVERVIEW

 

SPRING:  SY-U (second-year, sex unknown)

Overall appearance is of no help in identifying second-year Swainson's Thrushes, and there are no plumage differences between sexes.


Photo by Marcel Gahbauer, Las Caletas (CR), April 2008


There are often pale tips or shaft streaks on some greater coverts, and p10 (visible in the second photo) is relatively long and rounded.


Photo by Marcel Gahbauer, Las Caletas (CR), April 2008


Photo by Marcel Gahbauer, Las Caletas (CR), April 2008
 


The rectrices are relatively narrow and pointed, and generally in fair to poor condition.


Photo by Marcel Gahbauer, Las Caletas (CR), April 2008

RETURN TO AGE/SEX OVERVIEW

2002- The Migration Research Foundation Inc.