Thursday, July 28, 2016

Two Birds...?

Welcome to Two Birds, where I use my photos to compare two birds and talk about their similarities and differences.

This edition of two birds is not about distinguishing two different birds; rather, it's about realizing how different one bird can look depending on what time of year it is. It's also about connecting those initially different images to the underlying similarities that help us recognize when we're dealing with plumage variations.  

In light of the upcoming fall warbler migration (eeks I'm excited), this time I've chosen two birds that are actually one in the same. Warblers in fall can be tough to ID, as their plumages become less brightly colored and more difficult to differentiate. Still, when we keep in mind the "spring versions" of warblers when looking at them during fall, we begin to see how the two are connected.

Chestnut-sided Warbler (Setophaga penslyvanica) in fall (left) and spring (right) plumages
*Note, the fall warbler on the left does not have chestnut streaks along its sides, which means it could be a juvenile (first winter) bird. A fall bird with chestnut streaks would be an easier bird to positively identify as a CSWA (click here to learn more about bird name abbreviations, or alpha codes). 
**Also note, there are further plumage differences between male and female Chestnut-sided Warblers that will not be addressed in this post. For the sake of keeping this comparison simple, the characteristics discussed will be in reference to male birds only.
How to distinguish this bird in any season...

Visual Clues
  • Bright yellow/greenish cap with yellow extending throughout the back and into the wings
  • Diagnostic yellow to yellow/white wing bars
  • Very plain white breast and underside, including undertail coverts (UnTC)
  • Some fall birds retain some chestnut colored side streaks
  • Bright white eyering in fall which is mostly hidden by black mask in spring, especially upper portion
Behavioral Clues
  • Usually keeps to the middle to lower levels of greenery, not as high up in the trees as some warblers
  • Usually cocks its tail
Audio Clues
  • Click here for the Chestnut-sided Warbler's jaunty songs and calls  ♪♫ >(')

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