Arctic Tern - A Life of Ice, Light and Flight

On the afternoon of January 12, 2015 I was immersed in a surreal setting of ice, snow and water. We were just west of Booth Island and north of Pleneau Island on the Graham Coast of the Antarctic Peninsula. Above me in the clouds to the east were Mt Shackleton and Mt. Scott, but I had to trust the map to tell me that. There were no mountains to be seen that day. The clouds were low and large flakes of snow floated from the what was left of the sky, seemingly spontaneously forming just above our heads.

We were there because of the icebergs. This area is a frequent stop of tour ships because the currents and islands conspire to push icebergs into this area where they slowly decay into constantly changing abstract sculptures.
The day had started out with a curious Minke Whale checking out our Zodiacs as the staff prepared to transport guests to Peterman Island where we were able to visit colonies of breeding Gentoo and Adelie Penguins with a few Blue-eyed Shag nests in the mix.

Sandra and her friend the curious Minke Whale.

The afternoon was spent in the zodiacs, maneuvering through the shifting mountain ranges of icebergs, brash ice, and bergy bits to fully experience a true Antarctic spectacle of ice.

A chunk of bar ice where you can see how the water erodes small cup shaped divots from the ice. Photo by Sandra Petrowitz.

Perhaps just as interesting for me were a number of birds we found perched on the icebergs and feeding in their shallow pools. They were Arctic Terns and there were more of them in one spot than I have ever found on the Antarctic Peninsula. 

They were perched high on the ramparts of towering bergs in an Antarctic version of birds on a wire. 

The migration of this species is quite remarkable. They breed in their namesake region - the Arctic, but then migrate south through the Atlantic Ocean (and probably the Pacific Ocean as well) to spend their non-breeding summer in the Antarctic Pack ice. We know more about the portion of the population the migrates through the Atlantic through some interesting research conducted on Arctic Terns in Greenland and Iceland known as the Arctic Tern Migration Project. Below are a couple of maps that show the migration route and winter areas of the eleven birds they tracked (both images from the Greenland Institute of Natural Resources)

Simplified figure showing migration patterns of the Arctic tern, from the breeding sites in Greenland and Iceland to the winter grounds at Antarctica. After initiating the southbound migration (yellow line) the birds paused their migration in the central part of the North Atlantic (small circle) for almost a month before they continue towards the wintering sites at Antarctica (large circle). In spring, the northbound migration (white line) is conducted more than twice as fast in a gigantic “S” shaped pattern through the Atlantic Ocean. Areas particular rich in biological productivity are indicated by yellow and green colors.

Interpolated geolocation tracks of 11 Arctic terns tracked from breeding colonies in Greenland (n = 10 birds) and Iceland (n = 1 bird). Green = autumn (postbreeding) migration (August–November), red = winter range (December–March), and yellow = spring (return) migration (April–May). Two southbound migration routes were adopted in the South Atlantic, either (A) West African coast (n = 7 birds) or (B) Brazilian coast. Dotted lines link locations during the equinoxes.

As you can see from the map above, the wintering area for most of these birds is the edge of the pack ice in the northern part of the Weddell Sea. Presumably they spend their non-breeding summer much like I observed them - foraging among the ice in the open waters between the ice as well as the shallow waters formed by the icebergs themselves.

One iceberg in particular formed a spectacular eroded backstop for the foraging terns. 

There were a few other creatures foraging in the same area with the terns. We observed another less inquisitive Minke Whale that afternoon as well as a Crabeater Seal lounging in an iceberg pool and a few Kelp Gulls. 

So why did I see so many on this trip? One explanation is that I just hadn't been in the right place at the right time and they have always wintered in this area. However, I believe that this year the pack ice was so heavy in the Weddell Sea that there was essentially no open water and the birds wound up concentrating along the Antarctic Peninsula in numbers that would not be found during a "normal" year just to be able to find something to eat. 

Perhaps a more fitting name for this bird would be the Polar Tern, since they spend a majority of their life in both polar areas where they also experience perpetual daylight. The distances these birds migrate is impressive and when they are not breeding or wintering in the polar regions they are flying in a twisted migration loop back and forth across the Atlantic Ocean. 

Winter Greater Sage-Grouse

A couple of weeks ago I was in northeastern Montana for some meetings and I managed to carve off a few hours one morning for a quick trip out to an area where I knew Greater Sage-Grouse have wintered in the past. I also had a local resident tell me that she had observed a number of birds in the area recently so I was hopeful that I would run across a few birds.
The weather that morning was fairly nice but somewhat windy, which is pretty typical for that area this time of year. The worst part was that there was a pretty heavy overcast too, which didn't provide for the best light for photography.
I had to search quite a bit for any birds, but finally found a small group of about 5 birds just off the road, just as I was about to turn around and head back towards town. They got nervous when I stopped to watch them and they flew off a short ways to the south, making the rather miserable light conditions even worse as I would be looking directly into what light there was.
I moved off down the road a ways and pulled off to check to see if I had any phone messages and there they were. A large flock of about 80 birds just off the road, plucking sagebrush leaves from the exposed sage in the snow.

I am not surprised that I had a hard time finding these birds. They are very good at blending in to a snowy sage landscape.

 After a short while the bird relaxed and continued to forage in the sage next to the road I was on.

 Maybe next time I can find them with a bit more light to work with, but it certainly was a nice way to spend a morning.

More Pronghorn

Jack Frost descended on northeastern Montana with a scythe this year and he has been busy using it. I received word today that the Pronghorn deaths from train collisions in the last few weeks is now at least 700 animals across the the northern part of Montana.
As I drove south from Fort Peck to Billings this morning I witnessed first had that it's not only trains that old Mister Frost is using to exact his toll. Exhaustion and starvation are now coming into play full force. As I have mentioned before, the snow is deep and crusted and the last two nights the temperature had dipped well below zero, tapping even more energy from these animals just to stay warm. Forage is hard to come by and with well over a month to go before we usually have any relief with warming temperatures and melting snow, Jack is going to be busy in February.
In addition to the railroads, our highway are also one of the few places left where snow depth does not limit movement and the Pronghorn are using the roadways to move too. With the same results as the railways. I came across a number of spots where a vehicle had plowed into a herd of Pronghorn moving down the highway, resulting in twisted, frozen carcasses tossed in the ditches on either side of the road.
It has already been a long winter for these animals and it is probably going to get worse before it gets better. March and melting snow can't come soon enough.

Pronghorn update

Just couldn't do another Pronghorn in the snow photo so I am using this one to think of better days. I found out this morning that at least another 70 animals were struck by a train in one event this weekend, plus another 30 or so in a different incident. This pushes the known direct mortality from train strikes to nearly 400 Pronghorn in the last few weeks. Certainly there are additional indirect mortalities associated with these events along with mortalities associated with starvation, predation, and vehicle strikes that push the loss of animals even higher.
This is a killer winter where the impacts of landscape changes are most evident and detrimental for most of the big game animals in this area. Continuing changes to the landscape inhibit the movement of animals and leaves them stuck in areas where they are unable to survive. These changes are not as evident during most winters, but when the chips are down and the animals need to be able to move easily to survive, the impacts are amplified. The effects of these incidents and landscape changes on these populations is going to be felt for a long time.