13 April 2012

Earlier this week Libby Strizzi sent me an email with this ruby-throated hummingbird migration map and the question:  Why are the hummingbirds everywhere but here?

The map from hummingbirds.net is shown above with a black circle drawn to highlight the absence of hummers.  Hummingbirds have been seen east, west and north of northwestern Pennsylvania but not in the “hole.”

I’ll bet this is because northwestern PA is not on any spring migration flyways.

Migrating birds use four aerial “highways” to reach their breeding grounds in the spring.  Pennsylvania is fed by the Atlantic Flyway.  You can see this on the map below by Melissa Mayntz from her article 12 Types of Bird Migration at The Spruce.

Notice the “hole” in northwestern Pennsylvania where the migration highway splits into two streams.  Early migrants are probably following the main highway and not stopping in PA’s northwest corner.  Other migrants fill in the gap but they arrive later.

And notice that two flyways meet in northwestern Ohio at Lake Erie.  Two sources of birds!  That’s why birders flock to Magee Marsh, Ohio in May.

We’ll just have to be patient.  They’ll get here when they get here.

(Hummingbird map from hummingbirds.net.  Flyways map by Melissa Mayntz from The Spruce.  Click on each map to see the original in context.)