This web/mobile application provides the average spring and fall migration arrival dates for the commonly seen migrants in the BOS Study Region. This region includes Western New York and parts of nearby Ontario, Canada. We are making this resource available to the birding enthusiasts of the area free-of-charge.

The data used to calculate the average dates was obtained from the decades of records kept by the Buffalo Ornithological Society (BOS). Approximately 20 years of the more recent data was actually used in the calculations, favoring current trends.

This project was inspired by the fact that birders would often refer to the BOS Verification Date Guide to justify unusual (late or early) sightings. The Verification Date Guide was never intended for that purpose and was meant only to give date parameters of when a Noteworthy Sighting needed written or photographic verification to the BOS statisticians. The dates provided in this resource should give a more reliable idea of when certain species can be found entering or leaving the region.

Remember: these are AVERAGE dates. Weather is a key factor in bird migration and will have a bearing on their arrival dates. And sometimes, birds will just do their own thing, regardless of the weather or what their predecessors have done. Of course, any species that is significantly early or late should be carefully documented.

We've also included the taxonomy for each species in the search results. The taxonomy in this program is based on the Checklist of North and Middle American Birds, using the latest changes through the 60th supplement. You may find this feature useful all by itself.


To use the search tool, enter the ABA's 4-character alpha code for a bird in the text box on the Search screen and click the "SEARCH" button - OR enter the common name of a bird. You can even enter part of a name, such as "thrush", "warbler", or "flycatcher" to get more results. Below are the messages you might receive back from your search:

  • A date - this will be the AVERAGE spring or fall arrival date based on years of record keeping in the region.
  • Year Round - this species can be found somewhere in the BOS Study Region all year long, i.e. Red-tailed Hawk or White-throated Sparrow.
  • Probable Wintering Species - some species are too difficult to calculate a date for because they occur in winter as well as other times of the year. Many ducks and grebes fall into this category.
  • Uncommon or Rare - these birds are vagrants or occur infrequently in the BOS Study Region, i.e. Black-necked Stilt or White-eyed Vireo.
  • No Records Found - either your search didn't match up to a bird OR the bird has never been reported in the BOS Study Region before. Check your search phrase for spelling.

Use the link for THIS WEEK to get a list of migrant species that are due to arrive during the current week. Once you're on that page, you can click on the forward and backward buttons to scroll through the rest of the year. Weeks go from from Sunday to Saturday.


  1. Open Safari (iPhone) or Chrome (Android) and go to http://dates.bosbirds.com
  2. iPhone: Click on the icon at the bottom of your screen that looks like a page with an upward arrow
    Android: Expand the vertical ellipsis at the top right of your screen
  3. Select "Add to Home Screen"


As of this date (JUL 2019), we have all of the arrival dates completed for both spring and fall. Departure dates are a little more difficult and may be added some time in the future if there's a demand, but we suspect arrival dates are what birders are most interested in. Plus, we'd rather be out looking at birds!

Good Birding!
Willie D'Anna (BOS Statistician)
Sue Barth (Web Applications Developer)