Yellowlegs – but which one?

Yellowlegs! That’s the easy part of the identification when this long-legged wader turns up. It’s a common bird in many parts of North America but there are two separate species, and all US birders are well aware of the ensuing identification problem . In Costa Rica the Greater Yellowlegs (Tringa melanoleuca) is said to be the less common of the two, with the Lesser Yellowlegs (Tringa flavipes) considered a common migrant. Both species are found only rarely throughout the summer months.

I’m tempted to call this a rare bird in the Turrialba area, because sightings of both species have been quite scarce for lack of suitable habitat. So it was with considerable joy that John and I were able, after much head-scratching, to identify a pair of Greater Yellowlegs.

Yellowlegs, Angostura (1)

Anyone for a swim? Greater Yellowlegs at Angostura; photo by John Beer

A hot, sunny morning this week found us on the banks of the Río Reventazón where it flows into the Represa Angostura. Here suitable habitat for waders is usually restricted because of the high level of the water, but recently the national electricity company ICE has used heavy machinery to change the contour of the lakeside near La Florencia. This has created a sizeable area of shallow water suitable for waders. Here’s a general view of the Angostura Dam and lake taken from high up at Balalaica:

Represa Reventazon from Balalaica (3)

The area at bottom right is now even more suitable for wading species; photo by John Beer

We were concentrating on Snail Kites and a pair of Southern Lapwing when a fairly large wader moved off to our right. After much trekking through mud we were treated to very close looks at a pair of what we at first thought were Lesser Yellowlegs. Size is often hard to determine and we had no other nearby species to give us a comparison.

Yellowlegs, Angostura (7)

Yes, my legs are yellow., but look at my big bill. Greater Yellowlegs; photo by John Beer

For comparison purposes here’s a Lesser Yellowlegs at home in Minnesota in May of this year; note the slender bill and overall dainty appearance:

Lesser yellowlegs, Minnesota

Lesser Yellowlegs showing thin, black and shorter bill; photo by Larry Waddell

The length of the bill relative to the head seems the best way to distinguish and in the case of Greater Yellowlegs  the bill is also much thicker and often two-tone, not all black:

Yellowlegs, Angostura (6)

This Greater Yellowlegs posed very nicely; photo by John Beer

Our birds gave what seemed like a two-note call, rather disconcerting because this is said to be the call of the Lesser Yellowlegs. However, I recall from experiences in the USA that this method of identification is very fallible.

Here’s a final photograph of one of our Greater Yellowlegs:

Yellowlegs, Angostura (8)

Greater Yellowlegs surveys the water at Angostura; photo by John Beer

Costa Rican bird guide Guillermo Saborío has an extremely helpful high-quality photo of both species taken together. See the following link:

https://macaulaylibrary.org/asset/71461271#_ga=2.122660035.994272523.1541212603-276230366.1458961486

 

 

 

 

 

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