The forgotten island

So whatever happened to Catalina, you may ask? The last you, as a reader, heard was that the birds were double brooding and the migrants were passing through. Not to worry. We did not abandon that island entirely. Luckily one of our field assistants was able and had the desire to stick around and monitor our remaining nests. As it turned out, only two of the double-brood nests were successful and the rest were lost to predators. Sad maybe, but also very useful information for us as we are interested in per capita rates of reproductive output. The end result of the Catalina field season was that the average pair of warblers was able to raise 3 young to the point of fledging. Much better than last year, when we did not document any fledglings on the island!

If you read my previous posts, you may remember that very few nests were lost to predators in the first round of breeding. You may also remember that snakes were implicated as the primary nest predator on Catalina Island. So why the sudden increase in predation later in the season? Well, one possible explanation is that snake activity increased from the month of March to the month of May. Ectotherms like snakes rely on warm temperatures to heat their body and enable forays in search of food. As the breeding season progressed and the days became warmer, it is likely that snakes were moving across the landscape faster and more frequently - and, as a result, encountering more and more warbler nests.

If you amass hours and hours of nest videos, eventually you are bound to catch a predation event in action. Earlier in the season we caught a california kingsnake taking nestlings out of a nest, but the video was from too far a distance to be interesting beyond simple documentation of the event. But I am pleased to report that Dan (the field assistant who remained on Catalina) got some great footage of one of our last nests being discovered and subsequently depredated by a kingsnake. The nestlings were 7 days-old at the time, and as you will see in the video clips below they made quite the meal for the relatively-small snake. Enjoy!

Clip 1: The discovery


Clip 2: The meal

My northward migration

It has been nearly a month now since I arrived in Alaska. I said my goodbyes to the Catalina field site on May 14th, caught a ride into town bright and early the following morning, and left the island for the first time in exactly three months. Talk about culture shock. The traffic and smog of LA and the hordes of unfamiliar people contrasted starkly with the small community where I had been living in the rugged interior of Catalina Island. But I survived. A shuttle quickly whisked me from the ferry terminal at Long Beach to the airport terminal at LAX, and soon I was onboard a flight bound for Seattle. The plane took off to the west and, in a fitting departure from California, it flew up the coastline in such a way that I had an excellent view of Catalina and most of the other Channel Islands (see photo of Anacapa and Santa Cruz). It was official: I was headed north, leaving behind our southern birds to catch up with their boreal-breeding counterparts.

My northward migration was of much shorter duration than would have been the case for the birds. I had a 3-hr flight to Seattle, a 3.5-hr flight to Anchorage, and a 1-hr flight to Fairbanks. In Anchorage I met up with Jongmin and Brent, who had arrived on separate flights, and was quickly reminded of my new location in the far north. Standing in the airport terminal not 5 meters from us was Jeff Corwin, a popular television personality from Animal Planet. We learned that he had just returned from a stint of collaring polar bears further north. I can only presume that his trip had something to do with the then days-old news that polar bears were being listed as a threatened species in the US. Regardless, there he stood in front of us. Not bad for a first impression of Alaska.

Our plane touched down in Fairbanks in the wee hours of the morning and there to meet us was Helen, who had arrived a few days earlier. She drove our dreary-selves back to the cabin where we were to stay, and there we crashed after our long day of traveling. We awoke the next morning and, after having skipped one day of fieldwork, I found myself strapping on my hiking boots and harnessing my binoculars around my neck. The first day was easy: we got a tour of the study plot, checked out some singing males, and paid a visit to an active bald eagle nest. The females were still on their migratory journey so that left us with time to settle in and adjust to our new surroundings.

But the calm period did not last long. Jongmin spotted our first female on May 18th, a bird carrying black, pink and orange leg bands that had been given to her the previous year. She took a few days to recuperate from her series of flights north and began building a nest on May 22nd. The females that arrived in the days and weeks to follow quickly followed suit, keeping us on our toes.

We have done well so far, with 29 nests and counting. The earliest are on the verge of hatching and the latest are still lacking a complete clutch of eggs. They are not easy to find. Orange-crowned warblers here nest exclusively on the ground, and the females are skittish if they notice us anywhere in the vicinity of their nests. It is therefore of the utmost importance to hide ones-self in the bushes to find the exact nest location for a building female, a feat of concentration when faced with a swarm of hungry mosquitoes.

We are now bracing for the upcoming nestling period when we will be running around video-taping nests and measuring nestlings, not to mention trying to find the nests we have missed. I will try to post in the weeks to follow but I cannot make any promises! In the meantime, I will leave you with this photo of a busy beaver and you can think of us.