David Allen Sibley's Blog

Summary: In practice virtually all will be identified presumptively by range. Positive identification depends on careful analysis of details of song (but questions remain about variation in song). Positive identification of silent birds is not possible on current knowledge. The Warbling Vireos were considered a single continent-wide species until 2025, when two species – Eastern […]

This is a supplement to my post about identification of Warbling Vireos, which covers the basics of distinguishing them by song In 2025 AOS and eBird split Warbling Vireo into two species, named Eastern and Western Warbling Vireo. Differences in song provide the best way to identify the two species, but there is variation, including […]

This morning (Oct 13, 2025) my Facebook page was hijacked and is being filled with spam AI videos. I am waiting for Facebook to restore control to me. In the meantime please spread the word to ignore those posts, and check back in a few days. Thanks for your support and patience. Stay healthy and […]

The spotted thrushes are notoriously difficult to identify. Differences are subtle and subjective, the birds are variable, and it’s often difficult to get a good view of them. On top of that, the field marks that are most often mentioned are not always the most reliable, and this group of birds has been somewhat neglected […]

Possible? It might be, but most of the widely published “differences” are too subjective and/or too variable to be of any value. I dug into this a couple of years ago and discovered some details that seem more reliable, which are summarized in the one page file here (also as a pdf via this link: […]

I put together this matrix of variation in breeding plumage Rose-breasted Grosbeaks, showing the differences between each of the four age-sex classes. In this species it’s relatively easy to distinguish males from females, a little harder to distinguish one-year-old males from older males, and nearly impossible to determine the age of females. As in many […]

Estimating numbers of birds in flocks is a skill that we use a lot while birding, but something we rarely get to practice. And – it turns out – something we are really not very good at! I’ve put together a course that explains some of the science behind the challenge, offers lots of quizzes …

Test your skills at estimating numbers with a new course Read More »

  I’ve just posted about 30 original gouache paintings for sale in the shop. Most of these were painted in 2016 for the app Song Sleuth, and show portraits of common birds singing. The rest are from the early 2000s and were painted for the NY Times syndicated newspaper column “Sibley on Birds” that was …

New original art for sale in the Sibley Guides shop! Read More »

The 2023 Clements/eBird taxonomy update has just been announced, and the biggest surprise is that Cattle Egret will now be considered two species! Few people are familiar with variation in Cattle Egret, and while the split won’t have much impact on North American birders I thought it would be helpful to describe the differences. At …

Two species of Cattle Egrets? Read More »

In their 2022 checklist supplement the AOS voted to elevate the southwestern populations of Eastern Meadowlark to a full species, with the name Chihuahuan Meadowlark. it’s been recognized as a distinctive population for decades, usually under the name Lilian’s Meadowlark, but making it a full species raises the stakes and adds new emphasis to a …

Identification of the newest meadowlark – Chihuahuan Read More »