Do Saw Whets migrate?

Saw Whets have pretty interesting migrations. They are a migratory species, though that was discovered only in the early 1900s, as they migrate only at night, and are pretty darn hard to see to begin with. This is one of the reasons banding can provide so much information to scientists. Here is a great article about the discovery of their migration.

Here is a decent map of the areas that they inhabit and migrate to:

They don’t have set migration patterns, such as from Point A to Point B every season. They just kind of move to lower elevations or just south enough to get to where they find it comfortable. They are well adapted to cold though, so they can still breed farther north than most other birds if they want. Our vultures in North America do much the same. They migrate south enough to where they’re finding enough food and call that good enough.

Every 4 years though, there is what is called an “irruption” in migration. Here is a quick general article on irruptions that includes a bit about the Saw Whets. It looks to revolve around a cyclical process in rodent populations.

This article has some numerical data about migration numbers, counts by gender, and influence of the lunar cycle on migration.

She’s adorable!

I know I saw just about every owl is one of my favorites, but the Saw Whet is a little special. This post shared a great compilation image showing a random sampling of Saw Whets. They have such a great diversity of coloration and patterns. It feels like they are special snowflakes, no 2 are alike. As much as I love all the owls, I’d usually be hard pressed to tell 2 of the same species apart much of the time. That really makes them stand out to me, especially among the many little brown owls that I often feel even different species look too similar even if they are rather different in many ways.

They also have huge personalities that are far bigger than their diminutive size. Don’t tell them they aren’t ferocious hunting machines!

Is that weight loss normal? That’s, like, a 13% loss.

Normal SW weight is 70-120g for females and 70-85g for males. The page I grabbed that from says that’s 1 average lemon for a male and 1-2 for a female for reference. Average daily migration is 6.5 miles / 10.5 km, and they will take a weeklong layover when required to stock up on those important calories.

I found this study of Saw Whets from 1980 at Prince Edward Island, and they were finding a loss of roughly 0.3 grams per hour for the owl recaught within a 24 hour period. The one in today’s post must have eaten since the first catch, as the calculation would have it down about 43 grams.

Recaptured owls showed weight changes between capture and recapture. Some 63% lost weight, 29% gained and 8% showed no change. Among birds recaptured within 30 h of the original captures, (i.e., on the same or succeeding night), 73 had lost weight. There was a strong positive correlation between weight loss and number of hours between capture and recapture (R = 0.611, P < 0.001) for those birds which had lost weight, approximately 0.3 g/h. Birds caught more than 30 h later showed a less consistent pattern, but this is expected since these birds are more likely to have eaten in the intervening time.

That’s the only actual numerical data I was able to find. This news article talks about weight numbers some more with their local banding station, but it’s more general. Nice article though!

I got ticked last night. The algorithm actually recommended me something good. It was about a dozen pics from a Saw Whet banding station and had lots with their little butts sticking out of tomato paste cans that they use to transport them from the nets to the station, but the page refreshed and now I can’t find it again. I was looking forward to sharing them with you all! Hopefully I will find more.

I hope that answered many of your questions, and if I’m really lucky, will have given you more questions to ask about. Owls are really amazing!