Friday, December 30, 2011

...some don't

Although early arrival at a breeding cliff can be risky, it has its benefits too...there's usually no objection from other potential breeders, at least for a while.  Eventually though there's conflict at some level.  Most often disputes are short, vocal and without contact.  On occasion though a brouhaha ends in injury or worse.
7|H captured with leg injury in 2005, returned to breed in 2006 (A. Franke)
Territory holder 03 B killed by intruder in 2007 (A. Franke)
Life time reproductive success is real currency here, and where adult investment  (see weight loss) in offspring is within reason, eggs and young are closely guarded day and night. 

Female falcon threatening an unknown intruder (RECONYX)

The margins are narrow and the investment considerable.  All things being equal, adults arrive in late May, lay a full clutch of eggs by the middle of June, hatch their young in mid-July.  Rearing a brood of nestlings lasts 'til the last week of August, and fledglings remain near the cliff for another 3 weeks.   Birds leave for their wintering territories in the middle of September.

Although short, August nights are cool at 70 degrees north (RECONYX)

Some make it...some don't.

Remains of 8|U and 13 B on nest ledge, fate of  8|W (3rd chick) not known (A. Franke)
Some get a second chance...

August 20, 53 C at 35 days old on her nest ledge near Iglulik, NU.
Barry Robinson banded 53 C (and her 3 siblings) at 27 days of age on August 12, 2011.  She weighed 792g.  Three months later (November 11), she was recaptured in Mexico by Oscar Diaz.  She weighed 920g.

53 C just prior to capture in Mexico, Nov 11 (O. Diaz)
Once in hand, Oscar (a falconer and bander) realized that 53 C had frounce (Trichomoniasis), likely as a result of consuming an infected pigeon or dove.  The infection had advanced sufficiently to cause watering and swelling of her eye, and although necrotic lesions were apparent in her mouth, they were still quite small.

53 C immediately after capture in Mexico (O. Diaz)
Oscar treated the infection, and a month later began flying and hunting with 53 C.  She hunts at 940g, and will be released in April in time to migrate.

Oscar Diaz with 53 C 

It's not often you see a blue banded falconry bird, good to know she is in good hands.


Saturday, October 29, 2011

It's all in the fat

Much about bird migration remains a riddle, and the puzzle persists when, for example, landbirds undertake open-water crossings that require hour upon hour of sustained flight despite the availability of seemingly safer terrestrial routes or man-made structures on which to land. In the Gulf of Mexico, there are hundreds of active oil platforms and peregrines are known to use them, leap-frogging from one to next using them to rest, cool off or as place from which to capture prey.

Swordpress map and YouTube video showing rigs 1942-2005

Despite the presence and safety of the platforms, some birds crossing the Gulf of Mexico apparently ignore them. For example, after spending 3 days on the Louisiana Gulf coast, one of our birds (28 E) crossed the Gulf flying 540 miles in 11 hours. She spent that night on the Yucatan Peninsular, then once again made a non-stop flight of 430 miles in 12 hours crossing the Caribbean sea to Honduras where she remained relatively sedentary for the next 36 hours. Then ignoring Nicaragua, Costa Rica and Panama, she again traversed the Caribbean Sea making landfall in Colombia 650 miles and 28 non-stop-hours later.

Between October 19 and 24, she flew more than 1850 miles and crossed 1620 miles of open ocean in 51 hours of sustained flight.

1850 miles and three open water crossings (totaling 1620 miles) in 5 days

Fat reserves are critical to lowering the risks of migration in general and managing the risks of strategies like open water crossings in particular. Fat carries twice the energy compared to the same amount of protein or carbohydrate. So storing fuel as fat is smart - birds can reduce the weight they have to carry despite loading up on their on-board fuel. Smart too, because burning fat produces water - not enough to prevent dehydration, but enough to slow it down. For Arctic-nesting peregrines that lose body mass whilst raising broods of young, getting fat fast could make open-water crossing safer than it appears.

28 E feeding her 3 nestlings

Monday, September 26, 2011

Some Slack

Biologists welcome any encounter with the animals they study, but consider themselves particularly lucky when the same individual is encountered multiple times.  The odds of a re-encounter can be improved by marking animals that reliably return to the same breeding, stop-over or wintering sites year after year. 

Breeding cliffs in Arctic spring (J. Kennedy)
A great deal has been learned about peregrines because of their tendency to behave this way.  But it takes many years, a lot of birds, huge resighting effort and persistent people to build individual encounter histories representative of the peregrines in our study.

Hilde Marie Johansen with marked adult female (A. Anctil)
For example, at Rankin Inlet this spring we captured a female (banded A|X) that is at minimum 15 or 16 years old.  First encountered in adult plumage (likely 3 or 4 at that time) in 1999, A|X has been encountered on five other occasions during her tenure at Rankin Inlet.

We know quite a bit about A|X.  Over the years she’s been paired with several different males at three different sites.   Despite her longevity and ability to hold a territory, she’s a reproductive dead-end!  We have not banded a single nestling at the sites she has occupied – she failed even to lay a single egg this year and last. 

A|X, ~15 years old, but zero young (V. l'herault)
 Like A|X, few of our breeding birds are encountered elsewhere.  We have no idea where they winter or which migratory routes they use.  More than ¾ of the annual cycle of the vast majority of the birds we study is veiled from us…this is not so with “Joe’s Hag”. 
In 2 short years, the Hag has shown us that migratory routes between years are not necessarily fixed (first through Texas in 2009 and then through Florida in 2010),  and it’s clear birds that breed at high latitudes (69°N) do not necessarily winter at low latitudes (6°).

This year she identified for us what may be the outer limits for a peregrines breeding at the northern limits of mainland Canada.  It seems the narrow margins experienced by breeders far north of the Arctic Circle have at least some slack.

Her inward migration started normally. She departed from her wintering territory in Colombia in synchrony with other peregrines wearing GPS PTTs.  Her rate of travel matched those documented previously in our study and others.  She typically stopped for 2 or 3 days after a few days of back to back passage, including a 2-day stopover on South Padre Island where she had been trapped 19 months earlier.  Everything, it seemed, was going according to plan.

Then, in early June, soon after she crossed into southern Manitoba, the Hag’s rate of travel slowed dramatically, then stopped.  And to make matters worse, her transmitter entered “Hibernation Mode”, then  stopped functioning altogether. 

As usual, most birds arrived on territory in late May, but the last signal we received from the Hag was on June 10th at a location almost 1000 miles south of her breeding location.  She was at least 2 weeks late, her 2010 eyrie was occupied by Rough Legged Hawks, and the male with which she had been paired was also absent.  We were in the dark – everything about her was veiled from us once again, perhaps for good!

Spring survey in late May as peregrines arrive to breed (V. l'herault)
The possibility of a re-encounter seemed slight, but we needed to make sure and wanted (even more) one last shot at trapping her.  Mark Prostor had put the PTT on her and he was determined to get it off if at all possible.  He and Barry Robinson set out on August 5th, when most pairs are feeding young between 10 and 14 days old.

Here’s how Mark tells the story...

Getting to the Hag’s site is no easy task.  From our field cabin, it first requires a 18 mile ride in freighter canoe followed by 10 very rough “tundra” miles on Honda ATVs just to reach the band of cliff on which she may be perched.

The Coxe Islands from the Freighter canoe (M. Fredlund
We drove the cliff base surveying for any signs of raptors. Two sites that turned out to be Rough-leg sites initially raised our hopes, but 4hrs into the search our initial expectation that she’d not made it back seemed most likely.  As we approached the end of the long band of cliff, I decided to deploy our trap in an attempt to bring any not yet seen falcons to us instead…it was a long shot, and resulted in nothing.

Rough-legged Hawk (G. Court)

With cliff and options running out fast, it seemed like a good time to do nothing at all but wait, watch and eat lunch.   The trap got no attention other than that from Barry and me.  Then, over the sound of the wind, I heard what could have been the kak-kak-kak of a peregrine. 

“Barry, did you hear that?”

We both turned and saw a male peregrine land atop a large boulder, and perched below him was a female. We had a pair of birds, and the female was wearing a PTT.  Joe’s Hag had made it back, and she was defensive! Barry searched to the east.  I had not searched far west when I found the nest ledge with three “very” young chicks…the eyes of one had not yet opened.  The Hag’s brood was 10 to 14 day younger than most of the other broods we knew of.

The day was warm, but the age of the chicks left little time to trap the Hag.  She returned to the ledge 15 minutes after Barry and I had hidden ourselves, and it took only 5 minutes more to trap her.  She was in beautiful condition with no abrasions whatsoever from wearing the harness for over a year.  But, on the patagium of her left wing was a well-healed, but still apparent injury.  Could this have slowed her down in the spring?

On the way out we drove past the cliff. She was back at the ledge with her young.  The PTT felt damn good in my pocket.

Sunday, May 1, 2011

The "Hag" is coming...

Time, technology and luck have broadened our view of the "Hag's" life in ways that the critically important, but brief encounter with her on the beaches of South Padre Island in mid-October 2009 could never do.

The "Flats" of Padre (photo: P. Andreano)

For those unfamiliar with the Hag’s history, she was re-captured in 2010 breeding in the high Arctic, and spent last winter in northern Colombia. But with the Austral summer now over, she and thousands of other Arctic-nesting peregrines are focused northward intent on raising the maximum number of offspring they can. For that to happen, they must first fly several thousand miles, contend with uncertain weather, evade predators and capture sufficient numbers of prey to ensure they arrive in the high Arctic well nourished and ready to lay a full clutch of eggs.

One of the "Hag's" neighbors on a full clutch of eggs

The most recent data for the "Hag" indicate that she flew a little more than 700 miles in 5 days from her wintering territory through Panama and Costa Rica, and settled in southern Nicaragua for at least 36 hours.

Looking north from Colombia to Panama and Costa Rica

Although her current location is obviously tropical, it won't be long before she and and other Arctic-nesting migrants reach the still snow-covered landscapes of the sub-Arctic. They'll press onward leaving the snow-free zone far behind them.

MODIS (May 7, 2011) image of Churchill, MB (red dot), and snow and ice in blue, open water in black, vegetation in green.

All things being equal, the "Hag" will arrive at her nesting cliff to find many potential nest ledges drifted in with hard-packed snow, ponds and bays frozen solid and prey will be more scarce than at any other time of the year.

Still frozen spring conditions (Photo:B.Robinson)

Soon thereafter, with the sun positioned higher on the horizon and 24 hours of daylight, conditions become generally mild, which combined with prey-rich landscapes can turn the Arctic into a peregrine factory.


More soon on the Hag's progress.