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Posts Tagged ‘Predator’

This past week on Ship has been very similar to what has been going on at Metinic and PMI. Most of our days have been pretty dreary. On these foggy and rainy days we spend our time reading (A+ to Morgan for reading 8 books so far), eating snacks, catching up on sleep, writing letters, drawing, and staying updated on what’s going on in the real world. It is relaxing, but we’re anxious to get back out there and get a closer look on how our terns our doing.

When it’s not too foggy out, we are able to sit outside and watch the colony. We don’t sit too close because we don’t want to surprise or scare them. We’ve been doing this frequently to deter the Peregrine Falcon who has been stopping by from the island.

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Sunset view while watching for predators

Before the bad weather, we spent most days attempting to re-sight bands, making productivity plots, and trapping adult terns to band, measure, and weigh. To trap the terns we use a Treadle Trap. We first need to replace the eggs with fake eggs. This prevents the tern from damaging their eggs once he/she is trapped. After this we place a wired box over the nest with one end open. When the bird steps through the opening onto the pad, the door will shut and the tern is unable to escape. We quickly retrieve the bird to collect our data, put back the original eggs, set him free, and repeat. It was pretty cool when I got to hold and release my first tern!

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One of our productivity plots

The results from our GOMSWG census indicated that we have about 620 nests in total. Hopefully we’ll start seeing some chicks soon!

-Amanda

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Armed to the teeth: by the end of our owl adventures, there were 15 padded leg-hold traps on perches stationed around the island. Not all of them worked out so well, though; the owl actually perched on the taller trap on the left without triggering it!

Most people who do bird work get into a rigidly defined schedule. More often than not, it involves waking up early– often hours before sunrise– and going to bed early to accommodate for our early-bird hours. Seabird work here on the Refuge is a bit nicer, with our day officially starting at a relaxing 7:00 am. For the past few weeks, however, the Ship Island crew has had to turn our schedule topsy-turvy, thanks to a dastardly nocturnal visitor: a great-horned owl.

Kelby first spotted the owl on an inauspicious morning in late June. We tossed up a first round of traps that very day, but the owl didn’t return for almost two weeks! When it did return, we knew it had discovered the tern colony from the number of bodies left behind. Over the next few weeks, we gradually increased nighttime monitoring, starting with midnight trap checks and escalating until we had somebody present in a blind during every single hour of the night.

Thankfully, our efforts paid off. At 12:17 am on 7/21, as I was tucking myself into bed after the 9-12 blind stint, I received a phone call from Kelby: we captured the owl!

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Handling raptors is a bit different than handling little seabirds. For one, terns don’t have knives on their feet…

Our adult and fledgeling terns face predation from various birds of prey, and not all of them are equally problematic. We have near-daily predation events from nearby nesting peregrine falcons, which accounts for dozens of casualties over the course of the season. This doesn’t seem to disturb the terns outside of the five minutes or so that the falcon is present, however. The same goes for merlin, northern harrier, and even the occasional Cooper’s hawk that finds its way out to Ship.

Terns and other seabirds have evolved a colonial defense against aerial predation, accomplished by banding together to evade capture in spectacular dread flights or by chasing off the predator altogether with brutal dive-bombing and excrement-shooting tactics. Nocturnal predation, however, is a different game altogether; the adult terns panic when they are threatened by a predator they cannot see, and will simply leave the colony for the night if they feel unsafe. If an owl is visiting for consecutive nights, fattening up on a steady diet of tern chicks and fledgelings, the adults will eventually decide not to return the next morning at all. That leaves the entire year’s worth of chicks to starve and fall victim to plundering by gulls.

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Built to kill: with long talons, powerful feet, and a toe configuration that can rotate to restrain prey, owls are well-adapted to surprise prey under the cover of darkness.

It turns out that this particular owl has been visiting more than just Ship Island for its nighttime escapades. A brief trip to Trumpet Island revealed at least five gulls recently killed, and we have heard nighttime disturbances from the birds nesting on nearby East and West Barge Islands at well. Even though we will only be able to see the positive effects of apprehending the owl here on Ship, we can rest easy knowing that the threat to the other nearby seabird colonies has been mitigated.

What happens next? Our big “friend” spent the night here on Ship but was picked up promptly the next morning. It will spend the rest of the week in a fancy flight cage with a local wildlife rehabilitator until it’s time to drive far, far inland. The owl will be released at a lush forest camp teeming with plenty of non-seabird prey, where he can live out his days hunting responsibly.

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Roger hurried out for an early-morning pickup. Here, he pushes the boat off with the owl (left) safe on board.

That’s all for now. We’ll have one last update on island news within the week. Closing is on 7/26 (!), but work will continue right until the end.

Meredith, Ship I.

Bonus bird fact: the great-horned owl’s closest North American relative is actually the striking snowy owl. While they may seem quite different at first glance, they share many morphological and ecological similarities. This even includes those striking “horns”; if you see a snowy in the right wind, you might catch a glance of its miniature ear tufts.

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Hey folks! Jill and Morgan here! It’s been a surprisingly beautiful first week on Petit Manan Island; let’s hope it’s a sign for the whole season! The island has been lively thus far with approximately 200 prospecting Common and Arctic Terns, but we’re expecting many more to come! Although PMI isn’t the largest of islands, it still receives a good deal of visitors, especially early in the season when birds are migrating North – we’ve seen 61 species thus far! Not all our guests have been of the bird variety though; we also stumbled upon a juvenile Grey Seal on our rocky shores earlier in the week!

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Downy Woodpecker sighting!

The start of the season means preparing the island for all the work to be done in the months ahead. This means setting up observation blinds, for band resighting and future monitoring of foraging habits and chick health, as well as collecting marine debris, building burrows for Black Guillemots and Atlantic Puffins, and marking potential Leach’s Storm-petrel burrows. Daily Alcid counts from the top of the Petit Manan Light have also begun. On a windy day it can get rather cold up there, especially for Jill, who hasn’t quite gotten used to the Downeast summer having just returned from a seabird job in the Galapagos!

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Can you spot the Leach’s Storm Petrel burrow? We’ve been searching the island for these small holes in the ground this past we week, and we have found 170 potential burrows!

As we prepare ourselves for the research season ahead, the birds are doing the same. The puffins and guillemots are seeking out rock crevices and other sufficient and creative hiding spots for their burrows. The male terns are attracting their mates with a Sandlance dowry. The Common Eiders are seeking out areas of high vegetation to form their nests. And the Peregrine Falcons, Merlins, and gulls lurk about hoping to catch a bite to eat with all these new dining options in town.

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The Atlantic Puffins have already begun choosing burrows!

Till next time, here’s a joke to hold you over – Why did the Puffin have a stomach ache? Because it had Alcid Reflux!

Best,

Morgan & Jill

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