Falkland Islands: Monday-Tuesday, 13-14 December
By Keith Bildstein
It wasn’t supposed to be this windy!
The Falklands are known for their winds, especially in summer. But the winds that greeted us this morning were stronger than usual. And it wasn’t just us. Falkland Islands Government Air Service (FIGAS) had placed all inter-island flights on hold, and the gale-force breeze that we faced at 6am would eventually build to a hurricane-force wind by late-afternoon.
High winds or not, our goals for the day were to begin field observations in earnest, and a little wind was not going stop us from our appointed rounds.
An inquisitive Johnny Rook (Green right) waiting to be released after banding.
Last night we had decided that today would be a “scoping day,” an opportunity to determine where the rooks and vultures were, what they were up to, and how best to catch the rooks to individually color mark them. (We had colored plastic leg bands in hand and decided to use them while waiting for the colored alpha-numeric aluminum bands we are hoping DHL will deliver next Monday.)
It also would be the day we started assessing the feeding status of each bird that we saw. The latter was important for several reasons. Ostensibly, it would provide information on when during the day, birds would be easiest to trap: the assumption being that hungry birds would be easier to trap than satiated birds.
Assessing feeding status also would allow us to measure how much food was available to the birds. The later would be particularly important when our summer data were compared with the results of similar observations we plan to make next winter, at a time when young Johnny Rooks are thought to be food stressed to the point of starvation.
A sub-adult Johnny Rook with a full crop.
Fortunately, Johnny Rooks have crops, enormous bared-skinned holding sacks for food in their upper digestive tracks. The crops bulge beyond the throat feathers when filled, providing us the opportunity to gauge the status of their fuel tanks. Vultures have somewhat less conspicuous crops. The idea was to make the rounds of the Gentoo colony, find the rooks and vultures and assess whether their crops were “empty,” “half filled,” or “completely filled.”
Sunrise comes early in the Falklands in December. We were up at 4:20, and fed and showered in time to begin our first survey at 5am. In little over an hour we meandered through the 22 or so sub-colonies of Gentoo Penguins looking for rooks, vultures, and skuas. Although skuas were not one of our focal species, we needed to get a feel for population at The Neck, as these belligerent and sometimes predatory gulls compete with rooks and vultures both as scavengers and predators on penguins.
We saw six Turkey Vultures, seven Johnny Rooks, and about 40 skuas flying over or standing near the edges of the sub-colonies, which were spread across an area of almost half a square mile of sand dunes and peat hummocks. All of the rooks were juveniles or subadults, while all of the vultures were adults. The skuas, some of which were breeding at the site, included both adult and sub-adult birds. By 6:30am the wind had picked up considerably, it began to rain, and we decided it was time to retreat to the cabin for some hot tea and news of the building storm.
The winds continued to build over the day, and what initially was forecast as a Force 9 gale whipped it itself into a Force 12 hurricane by late afternoon. Walking back to the container cabin in late afternoon against 84 miles-per-hour head winds was about the same as running up a steep hill. It quickly became apparent why Olympic skaters race with their hands and arms tucked behind their bodies. It sure does reduce the rush of an oncoming wind.
By 6pm, the individual whitecaps we were seeing earlier in the day had all but disappeared into a continuous meringue that made it difficult to separate the sea from the sky. Walking outdoors was out of the question and we were beginning to wonder whether or not our container lashes would hold our cabin down. Darkness came none-too-soon and we woke the next day to winds in the 40-50 mph range.
We had survived the storm. But what about the birds?
Johnny Rooks lining up at the trap for the opportunity to become part of the study.
We were out again early, this time to catch some Johnny Rooks. Our plan was either remarkably simple or naïve. We would walk up to a group of the pathologically inquisitive birds, which had been approaching us to within a few feet since the day we arrived , set our trap, and catch a few of them. Oddly enough, the plan worked even better that expected, even in high winds, and even though most of the rooks had full crops, thanks to loss of so many penguin chicks in the storm the night before.
Our trap was both simple and sticky. The former meaning that it was easy to build, and the later meaning that birds going for the bait associated with it got “stuck” to it. The fact that the trap could be carried in a shirt pocket made it eminently transportable as well.
The “noose string” trap we used consisted of a series of 8-inch diameter, 80-lb monofilament fishing-line slip nooses equally spaced and securely knotted along a 6-foot-long piece of parachute cord. The noose string was set in a V-shaped, two-sided triangle with the bait (mutton in our case) spiked to the ground in the center. Birds approaching the mutton were supposed to become snared in one or more of the nooses.
And that is exactly what happened.
After about 40 minutes of trapping, we stopped at seven birds hoping that next week we’d catch the rest (a total of 20 was the limit set by the Falklands Government during this experimental stage of the work) and place the more permanent alpha-numeric aluminum bands on them. In the mean time, our plastic leg bands would allow us to assess the overall population size of Johnny Rooks as a result of resightings of them versus unmarked birds.
We returned to the cabin for lunch, and spent the rest of the day assessing crop fullness in the birds we saw and looking for the birds we had just banded. That some were now banded made us feel as if we knew them personally.
Tomorrow, the plan was to do more of the same minus trapping, plus some behavioral observations of scavenging behavior.
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