Friday, August 26, 2016

On my own behalf: Middleton Island, Gulf of Alaska (May 15 - July 15, 2016)

I recently spent some time on Middleton Island, a small (2x8km) and remote island in the Gulf of Alaska, in order to take care of some unfinished bussiness. It all went fairly well. This post contains an almost random selection of photos taken during my stay, as well as some words that touch the subjects of my work only slightly. More will come out eventually, but will need to be published on paper first…

59°29’N, 146°28’W is our destination…

The northern airstrip, facing south.

Sealions (mainly Northern Sea Lions Eumetopias jubatus and fewer California Sea Lions Zalophus californianus got recorded during my stay) made a comeback to the island a few years ago. Well, they try to make one, but regular human disturbance was likely the reason for them to abandon the north spit this summer and hang out on some smaller rocks offshore. This photo was taken during my single visit to the potential rookery, from larger distance than what was kept by most other island visitors… (perhaps time for some regulation here?)

The cliffs and slopes continue to erode. The past few years several landslides occurred, one of which took this large Red-berried Elder Sambucus racemosa (a well-known specimen for the older generation of seabird researchers, it was the one in use as boundry marker during counts) from the cliff at the south end and deposited it in the current lowland, where it was found flowering.

Most of Middleton’s largest Sitka Spruces Picea sitchensis appeared to be in poor condition. The oldest generation (now around 120 years old) are decaying and regeneration did not seem to occur within the past years. The monumental tree at the FAA headquarters blew over last winter, but its currently being held up by ropes.

The island’s Bald Eagle Haliaeetus leucocephalus population was booming; no fewer than seven pairs nested (six was the previous record). The platform pair raised three chicks this summer, while the NEXRAD radar on the left underwent major renovation. The first eagle pair nested on Middleton in the mid 1980's.

As usual, a few immature eagles remained on the island this summer, often harassing the kittiwakes in the former A.C.&W. station. There seems to be some movement among these birds, as some left and new ones appeared in the middle of the summer. I found one flying many miles offshore west of the island, eventually arriving to the island's north end. During the last days of June an adult bird arrived which was later seen battling with several of the breeding birds regularly, as it was trying to fight its way in the population.

If there’s one bird I can’t get enough of it’s the Tree Swallow Tachycineta bicolor… Only four pairs occupied the nest boxes this summer, fledging 18 banded chicks. Several unpaired males occupied boxes as well. There was still a lot to learn from those birds and a full report about the 2016 breeding season will appear on this blog hopefully this fall.

View from the largest tower within the former A.C.&W. station, facing south...

Facing northeast.

Middleton once held one of the largest Black-legged Kittiwake Rissa tridactyla colonies in the world. Their number dropped quite a bit during the past decades. On my last visit to the island in 2010, much of the southwest cliff was still occupied by them. This summer the few kittiwakes nesting on boulders in the lowlands exceeded the number nesting on the cliff.

A movie of this Wilson's snipe Gallinago delicata facing variable wind directions would have been a lot funnier, I guess…

My best shot of a Killer Whale Orcinus orca (or Loch Ness Monster?) while it was on a hunt for seals.

I spent a lot of time scoping out >10.000 Glaucous-winged Gulls Larus glaucescens in their breeding habitat, suspecting there had to be a different species of gull in there somewhere (besides Mew Gulls). I wasted my time and found none.

Never did I see so many white feral rabbits on Middleton. In the first decades after their introduction in 1954, white remained one of the dominant colors. Natural selection probably changed something (in particular after the appearance of Bald Eagles in the 1980’s?). Strange to see so many, while at the same time the eagle population experienced a record high. This individual was taken care off by a Glaucous-winged Gull, who’s appetite for Middleton’s rabbits appeared larger than before.

It always seems like the whole world comes together in a Black Oystercatcher Haematopus bachmani nest. Every Zen garden should have one.

Presumed Japanese tsunami debris, providing a shelter for rainy moments after counting the island's entire oystercatcher population.

Every year a new boat washes up. This is the latest addition to the Middleton fleet. Fancy...

The rusty remains of the WWII era cargo ship U.S.S. Coldbrook are still holding up… Sydney, seen here from the back, maintained a blog about her experiences on the island (and will do so again next year?). Check out the link to that somewhere on the right.

The presence of a Bald Eagle nest on the Coldbrook’s mast detered many Common Murres Uria aalge and Pelagic Cormorants Phalacrocorax pelagicus from nesting on or inside the wreck. It was obvious that most of the 1000+ Common Murres present this summer did not breed due to regular eagle disturbance.

Inside the back of the ship an old Common Raven Corvus corax nest was found (center back in the photo, now containing kittiwakes). Ravens made their first appearance on Middleton during winter 2009/10. Two were present this summer, but no nest was found.

The South Spit

A handful of Mew Gulls Larus canus nested on the spit. They’re easily distinguished from kittiwakes as they lack a soul.

After a mild winter, Pacific Wrens Troglodytes pacificus were extremely abundant. It appeared that all available habitat was occupied this summer. On good wren-years, accumulated driftwood on the South Spit is known to hold a single territory (note the singing bird on the first photo). This year two males were singing there regularly. Numerous nests were found in the driftwood this year ( inside the largest trunk on the second photo). I recall that after a cold winter, in 2006 only a few singing birds were heard. There are some unconfirmed reports of a die-off.

Part of the vegetation study I’m conducting are several exclosures, which are small fenced off squares allowing me to monitor the development of the vegetation in absence of the island’s herbivores. Previous winter several storms damaged the already rusty chicken wire, allowing some rabbits to enter. Thankfully this happened outside the growing season so no real harm was done to the project. Every summer a few uncommon plants grow within the exclosures. As in 2010, this Unalaska Paintbrush Castilleja unalaschcensis grew at the same place inside the same exclosure at the north end. The only other paintbrushes noticed in that area were the ones used by the contractors renovating the NEXRAD.

During summer the rabbits eat most of the island’s flowers. Besides growing within an exclosure, there are several other ways in which plants manage to remain present on the island. Some of them are simply too beautiful to get eaten, like these Few-flowered Shootingstars Dodecatheon pulchellum…

Wild-flag Iris setosa

Fischer's Orchid Dactylorhiza aristata

Some plants fight back: the known patches of the carnivorous Round-leaved Sundew Drosera rotundifolia, just north from the Dwarf Forest, were still there (and increasing?)

I was hoping to put a bit more effort in social hygiene during my stay this time, by taking a plunge in some of the island’s fresh water. Too bad Leeches Hirudenea sp. recently found their way to Middleton (at least I never noticed them before). They now occur in pretty much all fresh water bodies present on the island.

Lapland Longspurs Calcarius lapponicus are birds of the alpine tundra, but Middleton's north end still provides suitable breeding habitat to 8 – 9 pairs counted there this year. They were a bit more common during previous visits between 2005 - 2010, when territories were also found along the gravel roads further to the south.

This is as close as I wanted to get to the pair of Red-throated Loons Gavia stellata in the Loonpond. The first recorded nesting of this species took place here in 2005. In 2010 a second pair showed up along the east, in a pond at the end of the Dump Rd, but it did not nest. This summer no fewer than four pairs were present, at least three of which nested and these were all seen with chicks. Red-throated Loons are on Audubons’ 2016 Watchlist, so I informed them about this positive development.

Yellowlegs sp… Tringa sp. in the Military pond. I didn’t spend a lot of time looking for migratory species (the timing of my stay was well off for experiencing fall migration). However, I was informed that up north the ice melted early this spring, allowing many shorebirds and waders to move into and depart from their breeding areas relatively early this year. That may have been the reason why I still managed to get my share during the first half of July.

July 4: low tide 07:47 AM -98 cm (predicted), northeast intertidal area.

Whatever is left of one of the exposed fossil banks in the northeast, containing large numbers of marine shells. Only visible during the lower tides.

Chamisso's Cotton-grass Eriophorum chamissonis, on a late summer evening.

It was a fantastic experience being able to connect with Middleton again this summer, to be able to observe how things change in nature and understand the different timescales on which it all takes place. And find a few new things along the way... It was also very nice to meet up with some old friends I hadn´t seen in years and make some new international contacts as well. Thank you all for making my time on Middleton an escapade I shall not forget. I hope I manage to get out there again at some point in the future.

Thursday, October 15, 2015

The Tree Swallows (Tachycineta bicolor) on Middleton Island in 2015

Tree Swallows near the military pond. Middleton Island, June 23 2015 (photo by Angelika Aleksieva).

2015 was the seventh year of the Tree swallow (TRES) nest box project on the remote Middleton Island. The first nest boxes were put up there in 2009, allowing the projects' first two breeding pairs to nest there successfully that same year. Before these boxes were placed the TRES nested on the island irregularly between the 1950’s and 2002 in abandoned buildings, probably no more than a single pair. All of these buildings got removed before 2006, leaving the swallows with no place to nest. From the first two occupied boxes in 2009, the TRES population gradually increased to 10 occupied boxes in 2013, but it subsequently dropped to five occupied boxes in 2014.

Tree Swallow peeking out of nest box 7. Middleton Island, May 30 2015 (photo by Angelika Aleksieva).

During the breeding season of 2015 the boxes were not monitored (though I did finally receive some fantastic photos of the birds occupying them!), but thankfully by the end of the summer Scott and Martha Hatch inspected and cleaned out all of the 17 nest boxes and reported their findings to me (as they did last year). Their data show that in 2015 at least 7 boxes got occupied, 6 of which contained eggs and resulted in fledged young.

Nest box contents as found by Scott and Martha after the breeding season (nests need to contain a feather-lined nest cup in order to count as being occupied by a pair).

Scott and Martha provided photos of each of the nest boxes’ contents, making it easier to distinguish the presence of true nesting pairs from boxes that were only temporarily occupied (often by a solitary male).

An ‘unoccupied’ nest box: little nest material indicates this box was not in use by an established pair. Middleton Island, August 24 2015 (photo by Scott Hatch).

Nests from which young fledged are characterized by the presence of feces. Middleton Island, August 24 2015 (photo by Scott Hatch).

Distribution of used and unused TRES nest boxes on Middleton Island in 2015.

Unfortunately, due to the absence of nest box checks during the breeding season, no information is available on clutch - and brood sizes for 2015. However, the information gathered by Scott and Martha does show that the 2015 TRES population managed to recover from previous year’s low (as far as the number of breeding pairs goes). Although the numbers of eggs and fledged young remain unknown, the number of egg laying pairs and those fledging young in 2015 got close to the known record year (2013).

To what extend weather conditions were of influence on this breeding season remains unknown. Unfortunately, early in the season Middleton’s on site weather station stopped recording precipitation. This seems to be a reoccurring problem. For future analysis it would be useful to have access to correct climatic data for each breeding season.

Only time and continuing inspection efforts will tell how this remarkably remote and isolated TRES population will develop in the future. For this, the current 17 nest boxes will also need to stay available to the swallows. The photos that Scott and Martha took show that 6 – 7 years of Middleton’s harsh weather conditions have started to affect the boxes. In order to have them last for many more years, a paint job will become necessary in the near future.

Additionally, it could be questioned whether the number of nest boxes determines the maximum number of breeding pairs on the island. Although the boxes have been spaced by the recommended minimum of 100 feet (28 meters) from each other (with the exception of one or two boxes), a look at the maps of occupied boxes of the most successful years (2013 and 2015) indicates that these birds have a preference for nesting as far away from other pairs as possible. During my stays on the island I also noticed that some birds defended areas around their nest box much larger than the recommended 100 feet between two boxes. This could negatively influence the number of available nest sites and the total number of breeding pairs. Because of this, I doubt whether the 17 nest boxes will ever result in 17 nesting pairs. In order not to have nest box locations limit the number of breeding pairs, 2 – 3 additional boxes should be placed, away from the existing grids and solitary boxes (this would be preferred to replacing existing nest boxes). This might allow a possible further increase of the population to take place and be noticed more easily.

Tree Swallow carrying insects for its young. Middleton Island, June 23 2015 (photo by Angelika Aleksieva).

I thank Scott and Martha Hatch for their help, as well as Angelika Aleksieva for the photos she sent me.