The greater yellowlegs and lesser yellowlegs are one of the most confusing pairs of shorebirds, but it is possible to pick out characteristics that can distinguish between these two nearly identical species. By knowing what to look for, every birder can sharpen their skills and feel more confident when identifying yellowlegs.
It's possible to tell the two yellowlegs species apart if birders watch for these traits:
- Jizz: On the first impression, the overall jizz of the greater yellowlegs is a heavier, stockier, bulkier bird, while the lesser yellowlegs is more delicate and refined.
- Size: While it can be challenging to judge a bird's size, the greater yellowlegs is significantly larger than its lesser cousin, as well as having a wider wingspan and bulkier build. This is a great way to tell these birds apart in a mixed flock but can be less reliable if they are at different distances or only one species is seen.
- Bill: The greater yellowlegs' bill is roughly 1.5 times the length of its head, while the lesser yellowlegs' bill is barely longer than its head length. The greater yellowlegs' bill also has a very slight upturn and is thicker, particularly at the base, while the lesser yellowlegs' bill is straight and thinner. Both bills are black, but in the winter, the greater yellowlegs' bill lightens at the base to give it a two-tone appearance.
- Nostrils: If the bird's nostrils can be clearly seen, look for how close the facial feathers reach along the bill. On the greater yellowlegs, the nostrils are well clear of feathering, but on the lesser yellowlegs, the feathers stretch much closer to the nostrils.
- Flanks: During the breeding season, the greater yellowlegs has more extensive dark barring along its flanks, while the lesser yellowlegs has much plainer underparts. This can be deceiving, however, depending on the bird's posture, how the wings are held, and the lighting of a birder's view.
- Primary Feathers: When seen in profile, the primary feathers of the greater yellowlegs extend just to the tip or only very slightly beyond the tail when folded. The lesser yellowlegs, on the other hand, has slightly longer primary feathers that extend more distinctly beyond the end of the tail.
- Wings: In flight, the greater yellowlegs is more likely to show white speckles along the secondary feathers, while the lesser yellowlegs has much plainer wings. This varies greatly with the bird's age, however, as well as how worn the feathers are when the bird is seen.
- Voice: When these birds can be heard, the voice is a clear indication of identity. The greater yellowlegs has a higher pitched, more strident voice and tends to speak in 3-4 syllable phrases, while the lesser yellowlegs has a softer voice and favors 1-2 syllable phrases with a more hesitant tone.
- Foraging: While foraging along mudflats or wet edges, the greater yellowlegs is a more aggressive, frantic feeder, while the lesser yellowlegs has more sedate movements and longer pauses.
- Range: Both these birds prefer similar habitats and have a similar range. The greater yellowlegs, however, is generally more widespread and is found more to the north in winter than the lesser yellowlegs, particularly along the Pacific coast. During migration periods, however, the range is much more fluid and these birds often mingle in the same flocks.
See the table below for quick comparisons between greater and lesser yellowlegs characteristics.
Field Identification Tips for Yellowlegs
There is much overlap between the distinguishing characteristics for both the greater and lesser yellowlegs. Many times, just seeing one or even two field marks is not typically enough to feel confident about the correct identification for these birds. When watching yellowlegs in the field, remember these tips to be more certain about which bird is which:
- Use a spotting scope if possible and study the birds thoroughly, noting as many details as can be clearly seen to compare between them for appropriate identification.
- Compare individual birds to other nearby species to be able to judge their size more accurately, and use those comparisons for general measurements.
- Take the time to listen to recordings of yellowlegs' calls to become familiar with the two distinct voices, and listen carefully in the field to note which birds are making which noises.
- Practice shorebird identification as often as possible, not only with yellowlegs but with other sandpipers, plovers, and different types of shorebirds to get more experience understanding their peculiarities.
Most importantly, don't get discouraged if it is not always possible to tell the two yellowlegs species apart. Even experienced birders can have trouble with these confusing birds, but the more familiar you become with both of them, the more confident you will eventually feel with every yellowlegs you see.
Quick Comparison Chart
|Characteristic||Greater Yellowlegs||Lesser Yellowlegs|
|Jizz||Heavier, stockier||Finer, delicate|
|Size||Larger, wider wingspan||Smaller|
|Bill||1.5 times head length, slightly upturned||Roughly head length, straight, thinner|
|Nostrils||Well clear of feathering||Closer to feathering|
|Flanks||Extensive dark barring during the breeding season||Plainer with less barring|
|Primary Feathers||Extend just to tail tip or barely beyond||Extend distinctly beyond the tail tip|
|Wings||White speckles on secondary feathers seen in flight||Much plainer, paler wings in flight|
|Voice||High pitch, 3-4 syllable call||Softer voice, 1-2 syllables|
|Foraging||Aggressive, active and frantic||Delicate with longer pauses|
|Range||More widespread particularly in winter and northern regions||More restricted range|