BIRDS OF COSTA RICA

PHOTO LIBRARY

Red-eyed Vireo / Vireo Ojirrojo (Vireo olivaceus)

 

QUICK TIPS:
1) Check the iris colour - it is grayish-brown on HY/SY birds, and red on AHY/ASY birds; note that this is only reliable from summer through March; eye colour should not be used to assess age during spring migration.

2) Look at the upper mandible lining - it is pinkish-gray to white on HY/SY birds, and dark gray on AHY/ASY birds; note that this is only reliable from summer through February; mouth colour should not be used to assess age during spring migration.

3 In spring, look for molt limits among the secondaries - on SY birds there is little contrast in wear between the tertials and middle secondaries (all of which are fairly worn), while on ASY birds the tertials are considerably more worn and abraded than the middle secondaries (but all of which are relatively fresh).

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
Sexes identical.  Broad primary coverts with green edging, often a visible contrast among secondaries at s6/s7.
   

 

SY - U
Sexes identical.  Primary coverts narrow with minimal edging, secondaries relatively worn and uniform in age.

Ageing and sexing details:

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

 



RETURN TO AGE/SEX OVERVIEW

 

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

In spring, all ages and sexes of Red-eyed Vireo have a similar overall appearance, and it is necessary to view the wings and tail to distinguish among them.  However, sometimes SY birds will retain a somewhat brownish tone to the iris.


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


The primary coverts on SY birds are narrower and more tapered than on ASY individuals, and with little or no greenish edging.  The secondaries are uniform in age.


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


The rectrices are somewhat narrower on SY individuals than on ASY birds, and often are more abraded by spring (though the appearance of the tail in this photo is mostly due to it being a bit wet).


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

RETURN TO AGE/SEX OVERVIEW

2002- The Migration Research Foundation Inc.