Heerman's Gull

[OregonJunco]

I am sure I saw a Heerman's gull on the southern Oregon coast last weekend. It was sooty gray all over, with black legs and an orange beak.
I am a novice birder, and gulls are difficult for me to identify, but I was sure of this one, until I looked at a range map and discovered that this species is not found on the Oregon coast until late summer and fall.
Now I'm questioning my identification.
How likely is it that this bird was here at the wrong time of year? How accurate are range maps?

[Michael Frankis]

Sounds fine to me. The description fits. Also 'sooty gray all over' means it was a subadult or immature, not an adult (white head in April), and birds of that age are not yet breeding and more prone to wander outside of the normal range.

You'll probably see them quite commonly in late summer / fall, I saw dozens of them in northwest CA (Fort Bragg area) in September a couple of years ago. An odd lone bird in spring is perfectly reasonable - I might be doubting you if you'd claimed 10 in spring.

There's a very similar situation here with Yellow-legged Gulls in Britain, the peak occurs in late summer when they move north from the Mediterranean, but there are a few in spring too.

Michael