Cover photo: © David Ledig / U.S. Fish and Wildlife Service, 2006, some rights reserved.
When studying shorebird identification, I often found myself scratching my head – especially when it came to identifying two common, diminutive Bay Area sandpipers: the least and western sandpiper.
Peering through my binoculars at large groups of tiny peeps, my mind would second-guess itself: Those look like dark legs, but then again it is awfully muddy…
For those of you that may also be scratching your heads on the other side of your bins, I’ve created this post as a compilation of identification knowledge that helps me most when discerning between the two species.
I’ve separated the article into two birding scenarios: observing a group of birds that looks like the same species (of least or western sandpipers) or observing a mixed-species flock in which you have narrowed down the species to least or western sandpipers.
If you see a group of birds that looks like the same species of either western or least sandpiper:
Clue 1: Check out those legs.
The first field mark that I tend to go for in the least versus western species diagnosis is leg color. Western sandpipers have black legs, whereas least sandpipers have yellow legs.
Yet it wouldn’t be as fun if it were that easy. As nature will have it, these small shorebirds are often foraging up to their legs in water. Also, the muddy habitats that they dwell in make it easy for mud to cake on their legs – making least sandpiper’s mud-caked leg look deceivingly like a pair of western sandpiper legs.
Clue 2: What kind of habitat is the bird in?
As mentioned by Joe Eaton in his clever Bay Nature article “Meet The Smallest Sandpipers of the San Francisco Bay“, a tip for discerning between least and western sandpipers is to look at the habitat that you see the bird in.
Western sandpipers will often be found near the edge of water. Least sandpipers are more likely to be in vegetated habitat on ground further away from the water’s edge.
That said, it is important to note that mixed-species flocks are not uncommon – so be sure to pay close attention to the birds’ field marks.
If you see a mixed-species flock and have narrowed the species down to least or western sandpipers:
Clue 3: If the two species are side-by-side, also compare their sizes.
The “least” sandpiper, true to its name, is smaller than the western sandpiper – making identification a bit easier if the two birds are side-by-side.
That said, things become trickier when the species is being looked at on its own. For this reason, I would suggest relying on some tips mentioned previously to make a stronger case in your identification.
Clue 4: If the two species are side-by-side, compare their bills.
Western sandpipers have longer, thicker bills with a more blunt tip than the bills of least sandpipers. If you have the chance to compare the birds side-by-side, take note of how the western sandpiper’s bill also appears more “droopy” than a least sandpiper’s.
(Bonus): If you are surveying for eBird or another citizen science program, when in doubt just record the bird as “sp”.
eBird’s citizen science data contributes to research worldwide. Thus, it’s important to report exactly what we see and discern. This means that if you are in doubt, it’s better to err on the side of caution and report a “sp.” bird rather than guess just to settle on a species in your report.
There’s no shame in admitting that you weren’t able to tell the exact species identity – you are just doing your job as a careful and responsible citizen scientist!
Have any tips of your own? Comment below to add your take on deciding between least and western sandpiper!
Resources to Learn More
- Birding 101: Juvenile Least and Western Sandpipers by BirdFellow
- Meet The Smallest Sandpipers of the San Francisco Bay by Bay Nature
- Identifying Winter Sandpipers by The National Audubon Society
Answer to the photo above: least sandpipers!