BIRDS OF COSTA RICA

PHOTO LIBRARY

Chestnut-sided Warbler / Reinita de Costillas Castanas (Dendroica pensylvanica)

 

QUICK TIPS:
1) Look at the primary coverts - on HY/SY birds they brownish-gray with little or no edging and paler than the adjacent greater coverts, while on AHY/ASY birds they are blackish with grayish edging in fall sometimes faded and indistinct by spring

2) Check the tail - outer rectrices are relatively narrow and tapered to a point on HY/SY birds, but broad and rounded on AHY/ASY birds

3) Examine the flanks - FALL:  AHY males have relatively distinct and extensive chestnut markings, limited and indistinct chestnut can be seen on some AHY females and some HY males, and an absence of any chestnut can occur on AHY females, HY males, and HY females ... SPRING:  on females the chestnut is relatively narrow and limited, and on males fairly broad and extensive

4) In spring, look at the lores and moustache - on males they are black, while on females they grayish with some black

5) In spring, look at the crown - typically it is yellow on males, and green on females, though the distinction is not always clear and may depend on lighting

Note that there is a fair amount of overlap in plumages, especially in fall, and multiple characteristics should be assessed; for some intermediate individuals age and especially sex may not be reliably determined

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 - M
Yellow crown; solid black lores and moustache; broad and extensive chestnut markings extending past the legs; blackish primary coverts; broad and rounded rectrices
 
 

 

ASY - F
Greenish-yellow crown; grayish lores and moustache with some black; moderate chestnut markings; blackish primary coverts; broad and rounded rectrices
 
 
 
SY - M
Yellow crown; mostly black lores and moustache; broad and extensive chestnut markings extending to near or beyond the legs; brownish primary coverts
 
 
 
SY - F
Greenish crown; grayish or even whitish lores; grayish moustache sometimes with black flecks; limited chestnut markings; brownish primary coverts

Ageing and sexing details:

SPRING:  ASY-M (after-second-year male)

 



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SPRING:  ASY-F (after-second-year female)

 



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SPRING:  SY-M (after-second-year male)

 



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SPRING:  SY-F (second-year female)

SY females are the least boldly marked, with the lores grayish rather than black, and the chestnut sides.


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


SY Chestnut-sided Warblers of both sexes show a contrast between the paler primary coverts, primaries, and secondaries, compared to the darker basic or alternate feathers comprising the greater, median, and (not visible in this photo) lesser coverts. Note that, as in this photo, one or two tertials may be replaced also, contrasting noticeably with the adjacent unreplaced secondaries.


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


SY Chestnut-sided Warblers of both sexes have narrow and pointed rectrices, but the extent of white is somewhat less on females.


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

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2002- The Migration Research Foundation Inc.