Much has been written about the identification of Semipalmated and Western Sandpipers. Most of it focuses on minutia, those little differences in plumage that are indeed very helpful in distinguishing these very similar species. The problem is, in order to use all those fine plumage details successfully, a good understanding of how to age shorebirds is required. Rather than rehashing ageing criteria and plumage details, this article will focus on the basics: the more fundamental differences between Semi and Western that should be the foundation upon which any plumage-based identification is made.

Tigrina Times Online Birding Magazine Cape May Bird Observatory » Semipalmated and Western Sandpipers: Start With The Basics

So starts Michael O’Brien’s article at birdcapemay.org. With several recent Western Sandpipers being found in Lancaster County at Octorara Lake among flocks of Semipalmated Sandpipers, this is a skill that is very timely to pick up. While reading the rest of the article by following the link above will be the most valuable I will summarize below.

Western Sandpiper (WESA) is slightly larger than Semipalmated Sandpiper (SESA) but the difference is small enough that you would have to see the two of them next to each other to discern the difference.

The bill length difference that is often touted as a identification feature (WESA longer than SESA) can be tricky to see because male WESA and female SESA overlap in bill length.

In overall proportions, WESA tend to look front heavy, with a bigger chest, larger head and thicker neck. This causes them to stand more upright when at rest to balance.

Check out the full birdcapemay.org article for the entire thing as well as some excellent photographs.

Check out the Dig Deep blog for a great primer on shorebird feather wear and molt. There are some great animated images that show the effects of wear on feathers and the overall appearance of the birds. With southbound migration just beginning, its a good time to brush up on this.

Learning about shorebird molt allows you to make one of the easiest observations about the migration phenomenon; adults and immatures often migrate at different times, or use slightly different paths on their southbound flights

So, this fall when you are scanning through flocks of shorebirds, try to record numbers of adults and juveniles. Maybe you will find out something new about your favorite shorebird spots.

David Allen Sibley, author of The Sibley Guide to Birds, also writes a column for Birder’s World titled ID Toolkit. His latest column focuses on identifying juvenal birds by focusing on wing and tail feathers and he has several good tips.

1. Wait for an adult to come feed the young songbird. This can immediately solve the puzzle but this does not work so well if the baby songbird is a Brown-headed Cowbird.
2. A fledgling songbird goes through a molt soon after fledging and replaces many of its head and body feathers. Before this molt, it looks very different from what young birds look like during fall migration. It keeps its wing and tail feathers for about 12 months and these feather regions are often very similar to the adults. Concentrating on the tail and wing feathers will often reveal the birds identity.

So go out and try this out. Quite a few states are working on Breeding Bird Atlases so any juveniles you find can be reported to the appropriate atlas projects below.

Pennsylvania 2004-08

Colorado 2007-11

Ohio 2006-10

Solano Co. (CA) 2004-2009

Yolo Co. (CA) 2009-13

Delaware 2008-12

Indiana 2005-10

Massachusetts 2007-11

New Mexico 2000-10