Mini Migrant Wave and Fog

Here on Southeast Farallon Island during the fall songbird monitoring season, weather determines much of what we do because of the way in which it affects songbird migration. Based on work done by Pyle et al. (Condor 1993), migrating birds arriving at Southeast Farallon Island are strongly influenced by local weather conditions. During much of the fall, high pressure over the northern Pacific Ocean combined with low pressure over the interior of California creates a strong northwest wind with alternating clear skies and low fog. This weather syndrome keeps migrating birds near the mainland coast, both because the following wind allows the birds to keep migrating, and clear skies allow migrants to see and follow the coastline. Regardless of wind strength or direction, fog inhibits birds from finding the island, simply because they can’t see it. Therefore, these conditions, which are what we experienced for much of the latter half of August and the first two weeks of September, lead to very few birds arriving on the island. Very few birds on the island means that we get to do a lot of data entry and proofing.

However, this all changed on the night of the 11th of September, and when we awoke on the morning of the 12th we found a high overcast sky and light south to southeast winds. These conditions are created when a weak low pressure system moves in from the Pacific, and are typically present for just a few days before the northwest winds dominate once again. Migrating birds flying over this cloud layer at night are unable to see the land below, so when they drop below the cloud layer in the morning to find food, they sometimes find themselves over open ocean: a truly inhospitable landscape for a landbird. With this high overcast and decreased visibility, landbirds can’t see the mainland, and so are more likely to end up on the Farallon Islands. The following two days continued with similar weather, and culminated in a spectacular wave of migrants on the 14th, with small flocks of warblers and other migrants arriving almost continuously over the course of the day. Here are photos of a few of the expected western migrant species that showed up during those three days of good migrant weather.

 

 

 

Birds of the year on their first migration are inexperienced and are much more likely to end up migrating over open ocean. These birds comprise most of what we see out here on the island. In addition to the expected western species, we get small numbers of ‘vagrant’ eastern songbirds. It is these species that we get particularly excited about finding. A small proportion of hatch-year songbirds are genetically misoriented during migration and follow a predictable incorrect migratory direction. For example, a warbler from the northeastern United States that is supposed to migrate in a southeasterly direction will instead orient in a “mirror-image” direction, i.e. southwest, and thus eventually find itself flying over California. During the three days of light south winds that we experienced, we had relatively good numbers of these eastern warblers show up on the island, the best of which was a Connecticut Warbler found by Matt Brady up at the lighthouse. Also located were a Mourning Warbler, 3 Tennessee Warblers, 4 Chestnut-sided Warblers, 2 Magnolia Warblers, 2 Blackburnian Warblers, 7 Blackpoll Warblers, and 3 American Redstarts. Other rare eastern birds that showed up included 2 Bobolinks, a Chimney Swift, an Orchard Oriole, and a Philadelphia Vireo.

Some less common western migrants seen during these few days included a Black Swift that circled the lighthouse, four Vesper Sparrows, a Blue Grosbeak, a Purple Martin, a Baird’s Sandpiper, a Pectoral Sandpiper, and a Short-eared Owl.

Since those three days of spectacular migrant weather we have been back to northwest winds and fog with very few bird highlights. The most unusual birds since the 14^th have been a Dusky Flycatcher and a Northern Waterthrush, both found on the 22^nd of September. Consequently, we are back to doing lots of data entry and eagerly awaiting the next period of light winds and high overcast!!

The Fall Begins!!!

The transition from the Summer Seabird breeding season to the Fall migration period always comes during the second half of August. With the field crew change, so too do changes come over the Island. The breeding birds are finishing up their nesting activity, while seal pups born in June and July are quickly gaining weight. The alternating days of wind and sun and socked-in fog that generally characterize the summer season start to give way to calmer weather and high overcast typical of fall. Northern-breeding species of birds have begun their southbound migration; many stop off to visit the Farallones on their way to warmer wintering grounds.

The fall migration crew this year consists of biologist Jim Tietz, out for his ninth fall season, Matt Brady, back for his sixth fall, and Oscar Johnson, a Farallon rookie. We joined Jessie Beck, a seabird intern that will be staying with us until mid-September, to continue monitoring any lingering breeding seabirds. Our arrival on August 21st was uneventful, though one of the first landbirds we saw was a Least Flycatcher at the Heligoland Tree (the one Monterey Pine on the Island). It’s always great to start the season off with a vagrant!

Variable light-to-strong northwest winds prevailed during our first week on the Island. Although these winds tend to keep migrants onshore, a few did manage to come out for a visit. Notable were several Blue Grosbeaks, including four together, an early-ish Hermit Warbler, a family of Greater White-fronted Geese, three Long-eared Owls, and a few Sabine’s Gulls seen during seawatches. Oddly, despite being a relatively common bird in the Southwest, there are fewer records of Blue Grosbeak for the Island than there are of Least Flycatcher!

 

 We set up mist-nets at the Rixford and Coast Guard trees, in anticipation of catching and banding migrants, but to date the weather has not allowed us to open the nets much. Not only is this because high winds are not conducive to catching birds, but also because the strong northwest winds have kept birds away from the Island, so there have simply not been many birds to catch. However, we have managed to catch a few birds. The most exciting of these came on the first day we opened nets, when we caught one of the Long-eared Owls. Luckily, we had locking size-5 bands (big bands, much larger than the bands we use for songbirds), so we were able to band it, and now we look every day for our banded owl!

 

A few migrant insects rode some of the lighter winds out to the Island. The most exciting was a Gray Hairstreak butterfly that Oscar found resting on a Lavatera bush on the 24th. This species was last seen on the Island 7 years ago. Other, more expected insects included several Black Saddlebags, Blue-eyed Darners, and a number of Variegated Meadowhawks (all dragonflies), as well as daily counts of West Coast Ladies (butterfly) in the range of 7-15 individuals. Another unusual species of insect came with two Blue Dashers, a species of dragonfly that had, until 2008, only been seen once before on the Island; there are now about six records for the Island.

Although the bulk of migration has yet to come, we’ve found a few vagrants aside from the Least Flycatcher. During a lull in the howling northwesterlies of recent days, a young female Blackburnian Warbler making her first journey south paid the Island a short visit, while an American Redstart made an even-more brief pause at the Lighthouse. A skittish Lark Bunting lurked on the Terrace for two days as well. Although on the early side of things, these three species are regular during fall migration. Late August is a good time to hope for a truly rare bird or two also. Two such species did grace the Island briefly. On the 29th of August, Oscar found a small, green-backed hummingbird that, after giving us some quick looks as it drank from some flowering Lavatera, we determined was the Island’s sixth-ever Ruby-throated Hummingbird! After capturing the bird in one of our mist-nets and examining it in-hand, we were able to confirm the identity with 100% certainty, a rare claim indeed for California. Coincidentally, this was not the first Ruby-throated Hummingbird for California this year. One was seen at Keith Hansen’s Wildlife Gallery in Bolinas, Marin County, for a few days at the beginning of the month. Even the rarity of the elusive Ruby-throated Hummingbird, however, was no match for the show-stopping flock of White-faced Ibis that circled the Island several times on the 24th! While mainland birders may scoff at ibis in the face of a Ruby-throated Hummingbird, Faralloners know that, from an Island perspective, ibis are among the rarest of species to ever occur on the Island, in the company of such outstanding birds as Red-flanked Bluetail, Common Rosefinch and Golden-cheeked Warbler. Why might this be? Because, up until the 24th, there was only one modern record of White-faced Ibis, a single bird, seen in 1998! So far, Fall Season 2010 is shaping up to be a fantastic fall. Stay tuned for more vagrants!

In addition to the more sought-after vagrants, we have number of other interesting, or just plain photogenic birds and mammals around the island in the past week.

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Although Ring-billed Gulls are one of the more common gull species on the mainland, they are an uncommon species offshore, and therefore also uncommon on the Farallon Islands. This individual, a juvenile, is a somewhat early fall arrival.

Occasionally we get California Gulls with field-readable color bands. This individual came from San Francisco Bay, but we also get individuals from Mono Lake.

This is one of the many bleached hatch-year California Gulls that show up on the island. We suspect that many of these are from Mono Lake, which is supported by the fact that the two Mono Lake birds that we have found show this bleached plumage.

Although not a particularly exciting bird anywhere in California, Eurasian Collared-Dove only showed up on the Farallon Islands for the first time in 2006.  A pair of these birds spent the whole summer here this year for the first time. Will they breed next year?

Thankfully for us, these photogenic birds have been particularly common on the island this year. Our surveys over the past few weeks have indicated that their nesting activity has increased.

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In addition to the expected west coast subspecies leutescens, we also get a few of the gray-headed Great Basin subpecies orestera. This individual stuck around for about a week as it molted into formative plumage.

"My, what pointy teeth you have!"  Although Steller Sea Lions are larger and tend to dominate California Sea Lions, Stellers numbers are dwindling along the West Coast.  Several causes have been attributed to their decline including environmental changes in the North Pacific, overfishing, and pollution. California Sea Lion numbers, on the other hand, expanded rapidly over the last few decades following passage of the Marine Mammal Protection Act in 1972. 

Delving into the Gull JuJu Archives…

Here on the Island, we’ve noticed that the Western Gulls have a particularly unique and fascinating taste for edible-looking things and nest decorations. When walking through gull territories, one will often notice a collection of rib bones, regurgitated bits of plastic trash and other such goodies, brought back lovingly from the mainland, some 30 miles away.

Over the years, we’ve collected our favorite findings and stowed them away into the Gull JuJu Archives. Here is a peek into the various juju tastes….

By far, the most common juju items found are decrepit plastic figures. A variety of army men, Winnie-the-Poohs, Lego characters, rubber duckies and many more have found their way into gull’s bills and stomachs. Two of our particular favorites are the Beanie Baby fish with bulging eyes (top left) and the slightly terrifying plastic baby doll leg.

Gulls seem to display an affinity for small round things as well, in addition to particularly colorful items such as cocktail picks. The distances that gull juju travel also differ. On the left are pinniped tags from Antarctica, along with bits of sealion fur, and a mermaid pouch likely from a nearby beach.

 

 

Remember thinking that cutting up your credit cards and disposing of them in the trash will make them safely disappear forever? Wrong. Pocket contents are also a gull favorite, be it your keys, rolling papers or iPod slips. We find it all here.

 

Unfortunately, the odd fishing hooks, lures and squid lights are also found. Although the birds who brought them onto the island avoided the potentially fatal repercussions of these objects, many birds often don’t. Due to poor by-catch monitoring, little is known about how many seabirds are entangled in fishing nets and hooks every year, and what the impacts are on their populations. However, while these lucky birds evaded death, many with similar tastes do not.

And last, but certainly not least, the oddball egg is a rare find. Is this proof of a mysterious 14th breeding species, or merely just another bit of Western Gull JuJu?

Whale Town

Last week the clouds lifted for a few days allowing us a glimpse of life off the island. Not only could we see civilization on the mainland, but other marine life was suddenly visible. The most prominant visitors we had were the Humpback Whales.

Two Humpbacks near the Farallones

These whales are well known for their acrobatic aerial displays (breaching) where they jump, and often spin, out of the water. Although the function of this behavior is not known, it is thought to possibly be involved in communication and/or ectoparisite removal. In any case, it's always incredible to watch. From the island, we have seen numerous whales breaching, tail slapping and flipper slapping. Our high count of Humpbacks last week was 91 in a single day! The number of Humpbacks observed from the island varies significantly from year to year but in the last two years we have seen very high numbers here in the late summer and fall. The high count last year was 107 on Oct 8, the second most seen in a single day (highest count was 125 on November 8 1998). It is definitely unusual to see numbers this high already in August so we may still break the record.

Humpback Whale showing how it got its name

 
Humpbacks weren't the only cetacean species spotted from the island last week. We also saw Risso's dolphins, Northern Right Whale Dolphins, Gray Whales and Blue Whales.

Risso's Dolphins near the Farallones

Blue Whales are the largest animal to have ever lived on this earth and were once extensively harvested. PRBO began recording recording cetacean sightings from the Farallones in 1973, only a few years after whales became protected in the US. The first Blue Whale was not seen from the island until 1978 and our counts since then have documented an increasing number of whales present in this area. Our high count last week was 7 in one day!

Blue Whale back. It's hard to get a feel for how big there are from this.

Although its always a treat to see whales, seeing them in these numbers is especially thrilling. Humpbacks were hunted extensively in the early part of last century, down to perhaps as few as 1400 animals in the North Pacific. Once whales became protected, Humpbacks and other species began to recover. Currently, the North Pacific population is estimated to be closer to 20,000 with around 1200 of those in the California/Oregon/Washington Stock (http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/humpbackwhale.htm). Counts recorded from the Farallones have helped to document the increase in the Humpback population as well as other species of cetaceans.

Cassin's Auklet chicks are fed krill by their parents

The presence of this many whales is yet another indication that there is a lot of krill around. Humpbacks and Blue Whales are baleen whales which means they filter large amounts of water to gather up their small prey. Humpbacks tend to eat a variety of small prey including krill and small fish, but Blue Whales feed almost exclusively on krill. They are the Cassin's Auklet of whales. The only difference is they are about 3000 times the size of a Cassin's Auklet! The presence of Blue whales, and the fact that Cassin's Auklets are producing lots of fat, healthy chicks, indicates the high abundance of krill in the vicinity of the island.







Happy as the whale recovery stories are, significant threats to whales remain. We witnessed one of the most serious last week when we found a dead Humpback floating near the island that appeared to have been struck by a ship. There were numerous deep lacerations on the whales left side. As this incident demonstrates, ship strikes are still all too common and remain a serious concern and cause of mortality to many whales.

Dead humpback spotted near the islands

Lacerations on the left side of the whale likely from a ship propeller