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Osprey Nest Building Behavior

Dear Bird Folks,

How many families do Osprey couples raise each year? I’ve always thought they only had one, but back in August I saw a pair building a new nest near my house. Isn’t August a little late for Ospreys to start having another family?

– Dick, Yarmouth, MA


It’s not their fault, Dick,

I’m sure that Osprey couple you saw wanted their nest finished back in the spring, but this is Cape Cod. We all know it takes forever to get the permits needed to build anything. I’ll bet the birds were promised all of their paperwork would be completed by Memorial Day…but nobody said which Memorial Day. At least your Ospreys didn’t have to call a contractor. They’d have a better chance of hearing from Amelia Earhart than ever getting a Cape Cod contractor to call them back.

You are right; spring is when Ospreys should be working on their nests. In fact, the first thing a returning male Osprey does, even before he stops at the post office to pick up the mail, is to go to last year’s nest, make repairs and wait for his mate to arrive. Ospreys mate for life, but it’s a very relaxed relationship. They are only together during the nesting season. The rest of the year the two birds don’t see, talk or even text each other. Typically, the male arrives from South American first. Sometimes a young, unattached female will move in with him (which he doesn’t seem to mind). But that all comes to a quick end when his actual mate arrives. (Older females aren’t about to put up with any intruding Osprey hussies.)

The breeding season is short and the birds know it. After a few repairs to the nest, the eggs (usually three) are laid. The female does most of the incubating, but the male will also sit on the eggs while his mate takes a break to stretch her wings, grab a quick meal and use the ladies room. After hatching, the young birds are fed a steady diet of fish, fish and more fish. It takes nearly two months of constant fish eating, growing and parental care before the nestlings are strong enough to fly. But unlike songbirds, which typically leave the nest forever the minute they can fly, young Ospreys are homebodies. They remain on or near their nest and continue to beg for free meals from their parents. Over the next few weeks the young birds slowly develop their hunting skills, but they also continue to beg. (At this point in their lives they are much better at begging for fish than catching them.) By around the middle of August, the adult female can’t take the nagging anymore. She needs some “alone time.” So, with little regret, she heads south, leaving her kids in the hands of her mate. The male does the best he can to provide his offspring with a few last meals, and some parting fatherly advice. But then he too leaves and doesn’t come back. By Labor Day most of the Ospreys we see hanging around nest sites are confused young birds that are trying to figure out what to do next. It’s a bit sad to see the lonely birds sitting high on a perch, wondering where everyone went. But eventually they too get the urge to head out and make the long journey south. (This is when all of the area fish can finally breathe a sigh of relief.)

The Osprey nesting period starts in April and isn’t completed until nearly September. It’s a long process and there isn’t time for them to have more than one family per season. So, if Ospreys don’t have a second nesting, why did you see them building a new nest in the middle of August? There are a few possibilities here. One is that you are lying and made the whole thing up, but I don’t think so. I mean if you were going to lie about something, you’d likely save it for the IRS, not birds building a nest. A better possibility is that the birds you saw were juveniles. Ospreys don’t breed until they are three or four years old, although sometimes younger birds will pair-up and even do some premature nest building, but don’t actually lay any eggs. A more likely explanation is that your birds were a victim of July 4th’s Hurricane Arthur. The early storm toppled several area Osprey platforms and when the platforms went down so did the nests along with the chicks inside. (Stupid Arthur.) When an Osprey nest is lost mid-season the pair will occasionally build what is called a “frustration nest.” It’s a half-hearted attempt to re-nest; only this second nest will not have eggs. It’s simply too late for the couple to have a successful breeding season. The best they can do is create a new nest and hope it will be waiting for them when they return next spring…if another storm or a young hussy doesn’t get to it first.

Even though the nest you saw being built in August won’t be turning out any babies this year, Dick, there’s an excellent chance it will be productive next summer. Well, that’s assuming the Ospreys’ new nest finally wins approval by the town’s building inspector. Good luck to them with that.


On a different topic:

This is my annual end-of-summer warning about buggy birdseed. Summer is the breeding season for meal moths, and meal moths love both heat and birdseed. In fact, the seed you are using right now likely had moth eggs in it the day it was purchased. If it sits around for too long, the eggs will hatch and your seed will become filled with webs, moths and gross little worms. The best way to keep the bugs away in the summer is to buy smaller amounts of seed, use it up quickly and never store seed in your house. Okay? Don’t say I didn’t warn you.