Feeds:
Posts
Comments

Archive for June 4th, 2014

Getting a handle on how many terns are nesting on Metinic (or any tern colony) is fairly simple: count up the nests and multiply by 2. However, Metinic has two species of tern, Arctic and Common, and figuring out which nests belong to which species can be tricky.

Whose egg are you?

Whose egg are you?

Like most terns, Common and Artic Terns both lay their eggs in simple nests called scrapes. The eggs of both species are essentially identical – oblong, with brown spots on a blue, brown, or olive background.  Common Terns typically nest in grassier areas and have 3 eggs per nest.

IMG_4059 (800x600)

A typical Common Tern scrape

Arctic Terns prefer more open rock or cobble and usually lay only 1 or 2 eggs.

IMG_4058 (800x594)

An Arctic Tern scrape

However, it is possible to find an Arctic Tern with 3 eggs in its nest, or a Common Tern with eggs up on a rock, so these differences are not enough to determine whose eggs are whose. The best way to tell who laid a particular batch of eggs is to watch who does the incubating.

To do this, we begin by locating a group of nests visible from a blind window. We place a pink flag next to each nest whose species is unknown.  This helps us find the nests from the blind, since the eggs are very well camouflaged and the blinds are usually some distance away.

IMG_4055 (800x600)

There is a nest on the those rocks, I promise! Now just imagine trying to spot it from 20 feet away – the flags make life a lot easier!

Next, we hop into a blind, pull up a scope, and watch. Usually within a minute or two, adult terns will settle onto the nests and resume incubation. With a scope or binoculars, we can tell the adults’ species.

A bright red bill like that means this nest belongs to an Arctic Tern

A short, red bill like that means this nest belongs to an Arctic Tern

After that, we replace the pink flags with either a red flag (for Arctic Terns) or a blue flag (for Common Terns).

IMG_4056 (800x600)

A red flag, indicating an Arctic Tern nest

So why is all this important? Once we’re done flagging nests, we’ll gather all the flags back up and tally up the number of Common versus Arctic Tern, then use our census number to estimate how many of each species we have on the island this year. For example, last year we marked 64 Common Tern nests and 37 Arctic Tern nests, or 63% Common and 37% Arctic. Our mid-June census found 330 total nests on the island, so we estimate there were 209 Common and 121 Arctic Tern pairs nesting on Metinic last year.

We’re excited to see how our numbers compare to last year!

– Amy

Advertisements

Read Full Post »

What is that sound walking to the outhouse in the dark of night?! It’s a Leach’s Storm-Petrel! Its call is a spooky one to hear for a person like me unacquainted with the “giggling” sound. I heard my first petrel call here on Petit Manan. Pretty cool!

While the other inhabitants of the island are roosting at night, Leach’s Storm-Petrels are active searching for a mate and a burrow dug from the soil. They are a secretive, nocturnal, and pelagic species only returning to land to breed and active at night to avoid predation. Petrels lay one egg that is incubated for 37-50 days and chicks fledge in September or October.

new5

Julia with a Leach’s Storm-Petrel adult

Early in the season, we venture out in search of petrel burrows. Our goal is to mark 20 active burrows with colored flags. How do you know it’s active? You reach into the burrow (1-3 feet in length) to find a nest cup, nesting material, or a petrel! Often burrows curve, so a burrow camera can be used to reach where your whole arm cannot. One indication of Leach’s Storm-Petrels is their musty smell at the entrance of a burrow.

Image

Wayne smells a petrel

Image

Burrow entrance

Image

Julia holding the camera and Anna wearing the viewing screen

Image

Burrow camera in use

Later in the season we will return to the flagged burrows and determine the presence of an egg. Then return again to check for a hatched chick. In the meantime, we will continue with our tern and alcid activities. Look for Petit Manan’s next post for some exciting news!

-Brittany

Read Full Post »