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Sunday, April 22, 2012

The Osprey Files: An Attempted Nest Takeover

The news from the Maine coast: our Osprey couple has survived an apparent nest takeover this week.

A few days ago I spent a few hours watching the nest. The female, Wapatewi, still spent most of her time incubating eggs while the male, Notenwi, hung out on his favorite roosting tree on the far side of the island.  After a long stretch of no activity I decided to call it a day and head home. I started packing up my camera when Wapatewi, still on the nest, began screeching to her mate. I thought that maybe she was simply hungry - she tends to squawk to her mate when she needs food and he obligingly flies off to go catch a fish.

But this time things were different.

Notenwi flew off his roost but instead of heading off to catch a fish, he began circling higher and higher over the nest. At the same time, Wapatewi screeched more loudly and turned to look not at her mate, but westward, over the mainland. She was obviously stressed about something.

Then another female Osprey appeared, flying in from the west and attempting to "dive-bomb" Wapatewi as she guarded her eggs! I looked into the sky for Wapatewi's mate and saw him chasing off a male Osprey.

The interlopers appeared to be trying to take over the nest. The new female repeatedly flew in close to Wapatewi, almost seeming to bully her and likely trying to get her to abandon the nest. For her part, Wapatewi stood her ground without leaving the eggs, scolding the intruding female sternly the whole time.

Wapatewi scolding an intruding female Osprey

Notenwi successfully chased off the new male Osprey, then flew back to the nest to take on the new female. A couple of circuits around the island with Notenwi on her tail convinced the intruder to give up and follow her mate to another location. As soon as the second Osprey was out of sight, Notenwi settled back down on his favorite branch and Wapatewi went back to the business of quietly incubating her eggs.

As all of this was going on in the skies above us, a small crowd of people had gathered to watch the confrontation. I guess because I had a camera and some sense of understanding what was happening, folks started asking me about this behavior and if it was "normal."

What's going on is that nest sites for Ospreys are at a premium. Think of them like custom-built homes - each one takes a pair of Osprey many, many hours of effort to build. With coastal development here in New England, many of the big, old trees that used to support nests have been removed. And natural processes destroy trees and nests too - one big winter storm can badly damage or destroy many Osprey nests within the space of hours.

On the plus side, humans have been building artificial nesting platforms all over New England - and Ospreys have been using them. But still, nests are hard to come by, especially for young Osprey pairs just starting their lives together.

Ospreys tend to mate for life and many of them return to the same nest year after year. It looked to me like Notenwi and Wapatewi had been together for a while - their communication was superb and their "changing of the guard" while incubating eggs was always smooth and efficient. I'd also sensed that they'd used this nest before - perhaps for several years. They seemed really familiar with the area and were already incubating eggs - they were weeks ahead of the other birds passing through.

This last week has seen a peak in Osprey migrations through New England (Osprey that nest in the northern US and into Canada winter either in Florida, Central, or South America). This intruding pair was likely migrating through and looking for a suitable nest site. If they could scare Notenwi and Wapatewi off their nest, the new couple could move in and start their family right away, saving weeks of effort in finding or building a nest.

Instead, the new Osprey will have to look elsewhere. Notenwi and Wapatewi have too much to lose to give up their nest without a fight.

Text and photos copyright Nancy Rynes, 2012. You may link to this page but you're not allowed to copy any portion of it without my express written permission.

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