Saturday, September 28, 2013

Blue-footed Booby Invasion Finds The Farallones

On August 25th, some tourists visiting the east side of the Sierras took a photograph of a strange bird on the shoreline of Mono Lake. Later that day, they showed it to Max Henkels, an intern who was leading a bird walk for the Mono Lake Committee. He immediately recognized the bird in the photograph as a Blue-footed Booby. He was likely very excited, as this species had never been recorded at Mono Lake. Unfortunately, the bird was never re-found by Max or any other birders or biologists. The tourists then left town without leaving any contact info and the photo was lost. However, this story was only the first of a series of Blue-footed Booby sightings in California this year. An unprecedented number of Blue-foots have shown up all over the state since this first individual was spotted at Mono Lake.

Over the next several weeks, dozens of Blue-footed Boobies were reported from coastal and inland Southern California. By September 11th, they had reached Northern California. A single bird was spotted by birders Mark Butler and Roger Harshaw at the Point Reyes Lighthouse; and in the following days there were sightings from San Mateo, San Francisco, Marin, and Sonoma Counties. Astoundingly, a single bird was found all the way up in British Colombia! On the Farallones, it was only a matter of time before one showed up here.

A map showing the locations of all Blue-footed Boobies reported to eBird so far in 2013.

Finally, on September 18th, a call came over the handheld radios on Southeast Farallon Island that a Blue-footed Booby was perched on the western edge of Saddle Rock. Moments later, everyone on the island was peering intently through binoculars, cameras, and spotting scopes at the Farallon's first ever Blue-footed Booby. The juvenile bird preened nonchalantly before taking a short flight and landing back on the rock, never suspecting how special the humans on shore considered it to be. It was quite a relief for us to finally see one after reading so many reports from the mainland.

The first Farallon record, pictured here, had a thin white stripe down the center of its tail, making it distinguishable from the rest of the Boobies to follow.

The second Farallon Blue-footed Booby showed up in the same place on the west end of Saddle Rock, an islet off the south end of our main island. The central tail feathers on this bird are dark, showing a different pattern from the first bird.

Cameron snapped off a few shots of this third Island Record Blue-footed Booby as it flew in during his sea watch. The longer central tail feathers (rectrices) distinguished this bird from the previous two individuals.

Can you spot the Booby amongst the Brandt's Cormorants? We are currently trying to determine if this booby is the same individual pictured above, in flight.

One more of Cameron's shots of the 3rd (or possibly 4th) Farallon Blue-footed Booby.

The California Bird Records Committee's publication Rare Birds of California tells us that Blue-footed Boobies breed in the tropical Eastern Pacific Ocean. Off their breeding colonies, they can be found anywhere from Baja California to Chile. However, they are known to periodically irrupt north into California and Arizona between July and October, during their post-breeding dispersal. During these irruptions, there have been relatively few records from coastal California. The bulk of the sightings (7 of every 8) have typically occurred many miles inland, at the Salton Sea, not far from the Mexican border and their breeding grounds in the Gulf of California. For example, in 1972 a flock of about 40 Blue-footed Boobies was seen at the north end of the Salton Sea at the Whitewater River delta. Prior to 2013, it had been over 30 years since the last irruption, which was minuscule in comparison. This time around, Boobies have been detected in at least 15 California counties, as well as Arizona and New Mexico, not to mention in much larger numbers. 

 On 24 September, Oscar Johnson made a conservative high count of 26 Blue-footed Boobies at the south end of the Salton Sea. How many of them can you see in his photo above? The next day, birder Dave Goodward saw 47 at the Whitewater River delta! This was the highest count ever recorded in California for Blue-footed Boobies.

The Farallon bird marked the fifth Sulid species to occur on this island, since biologists began keeping track of such things in 1967. Sulids, or members of the family Sulidae, are large seabirds with long wings, wedge-shaped tails, and stout, conical bills. Sulidae is comprised of ten species of Boobies and Gannets in three genera, but only five have been seen in North America. Remarkably, all five of these species have now occurred on the Farallones. Northern Gannet, Red-footed, Brown, Masked, and now Blue-footed Booby have all been seen from this tiny rocky island.

Last year, the birding world was shocked when Farallon biologists located a Northern Gannet on the island. Not only was the Gannet a first Island Record, it was the first to ever be spotted in the Pacific Ocean. The Gannet has been sighted roosting at the island nearly everyday since, and it is still seen daily, roosting on Sugar Loaf. Check out the Gannet story by clicking here.

This is one of my many photographs of the Farallon Northern Gannet from Fall 2012. Hundreds of people have visited the island on tour boats to get a glimpse (or some photos) of this amazingly rare bird.

The name Booby comes from the Spanish word bobo ("stupid", "fool", or "clown") because the Blue-footed Booby is, like other seabirds, clumsy on land. They are also regarded as foolish for their apparent fearlessness of humans. Sailors thought them unintelligent due to their habit of landing on boats at sea, where they were easy prey and inevitably ended up in the hungry seamen's cook pots.

Here, a Brown Booby takes a free ride to the Farallones aboard a fishing boat during Fall 2012.

So if you are interested in seeing some Sulids for yourself, and you live in California, now is the time to get to some rocky coastline and scan for Blue-footed Boobies. After all, it may be 30 years before they come back.

Friday, September 06, 2013

Covered in Flies

In a season that is usually highlighted by migrant birds and rare vagrant species, this incipient fall field season has been anything but, and to our chagrin, our attention has been focused on something entirely different. Since the arrival of the fall bird crew, Southeast Farallon Island (SEFI) has been inundated and plagued by a surfeit of flies. If any bird were interested, SEFI would be the ultimate buffet, but unfortunately there just aren’t enough migrant songbirds (thanks to the current weather pattern) to put a dent in the daunting number of flies. As they have spread over the island in one of the worst excesses seen in recent years, our incessant swatting, slapping, and twitching is driving us all mad. Being field ornithologists, 75% of our work requires us to be outside. To deal with the horrendous nuisance, we take preemptive measures to cover every inch of our bodies, even on calm, hot days, by tucking pant legs into socks, cinching sleeves tightly around gloves, and wrapping bandanas around our faces. Alas, the flies still manage to crawl under our protective layers to tickle us until we smash or release them. Imagine the perseverance it takes to stand motionless in a swath of flies for an hour conducting a bird survey. Quite frankly, the flies are wearing on us.

For healthy birds, the flies provide a much needed snack.  For a sick or weakened bird, the flies turn the tables and swarm the moribund individual. Take for instance this recently fledged Western Gull that has clearly lost the battle to live. 

A few of us have found a comical, to some vile, way to handle the flies. Ryan Potter, the carryover seabird biologist, has decided that letting the flies run amuck is the best way to overcome the problem. He theorizes that by exposing more skin, there is an overstimulation that is easier to deal with than just one or two flies crawling under heavier wraps. Thankfully, there are days when the flies don’t seem as bad and being outside becomes bearable. This mostly occurs when a steady force of wind keeps the flies clinging to the rocks, or when a cold fog keeps them at bay. Unfortunately, these are not the conditions that bring songbirds to the island. The few birds that are on the island, though, are making the most of this fly cornucopia, such as this Townsend’s Warbler making a tasty afternoon snack out of this hapless bugger, or this juvenile Western Gull picking away at a fly-covered sea lion corpse.  

Prior to writing this blog, it was assumed that the pest we were dealing with was the widely dispersed kelp fly, Coelopa frigida. This species of fly is common along beaches where it utilizes deposited kelp or seaweed for its reproductive cycle. However, thanks to a bit of recent sleuthing, we now know we are dealing with a completely different species. And it makes sense. SEFI is a rocky outcrop with little area or space for kelp to deposit, and kelp flies don’t tend to display the relentless desire to land on humans in massive numbers anywhere else. In fact, the fly that has proliferated on SEFI is better known as a Cormorant Fly. The species we appear to have here, Fucillia thinobia, primarily lays its eggs on dead cormorants and is only found near cormorant colonies. Dr. Robert Kimsey, an entomologist from UC Davis, recently studied this fly on Alcatraz Island in the San Francisco Bay, where it annoys tourists, and discovered the link between this species and cormorants. As it turns out, Alcatraz is also experiencing a profusion of flies and recently posted the following advisory: 

Visitor Advisory – Why are there so many flies on Alcatraz Island and on Alcatraz Cruises vessels?

During this time of year (September & October), one of the 17 identified species of flies on Alcatraz Island is found in large numbers around the dock area and on Alcatraz Cruises boats. These flies are commonly referred to as Cormorant flies, and they do not bite or pose a health risk to island visitors. The presence of these flies is an indicator of a healthy population of cormorants on the island. In the last two years, the cormorant population on the island was decimated by several natural events. This year, the population is rebounding, so the fly population has temporarily increased. These flies are a very important part of the island ecosystem and are not caused by any adverse conditions on Alcatraz Island or on Alcatraz Cruises vessels. We apologize for the annoyance these flies may cause and hope you will enjoy your visit to Alcatraz Island.

Because the type-specimen (the first of a species to be collected and described to science) of Fucillia thinobia was collected on SEFI, we currently believe that Corm Flies are also pestering us. In terms of its general biology, the adult flies deposit their eggs on dead cormorant bodies, and the larvae feed and mature in the guano-stained soil. One thing that makes this species of fly unique from other types of carrion flies is that it specializes on a specific type of carrion. By restricting itself to a particular group of birds in a seabird colony, the Corm Fly has evolved to take advantage of a predictable time and place of high mortality (many seabird young die before fledging) where it may reproduce. Here on SEFI we have three breeding species of cormorants with the most populous being the Brandt’s Cormorant. With 2013 being an early breeding season for seabirds in general and a rather productive year for the Brandt’s Cormorants, this year produced a bumper crop of corm flies. And with the seabirds having recently fledged, it appears that the flies may be exploring the rest of the island for a secondary host in which to lay their eggs. 

Now that we know the species we are dealing with, we may begin to search for answers to our many burning questions. For example, why are adult corm flies attracted to humans? It has been proposed that perhaps they land on humans as they would on any other substrate, but it is obvious to us that they swarm on us in much higher concentrations than on the surrounding substrates. So, are they attracted to us because we smell like carrion? Perhaps they wish to lay their eggs on us and this is just a case of mistaken identity. Originally we wondered if they could be feeding on us, but we do not observe them “licking” us with their proboscis (fly mouth-parts). Either way, we have found, as you may have wondered, showering does not deter them from swarming on us.

It is also apparent that some years have more flies than others, and it would be interesting to know exactly what factors affect their population. Is it just numbers of cormorants breeding, or do Corm Flies reproduce in greater numbers following a couple years of poor cormorant productivity? The last really big year for Corm Flies was in 2004, and an intern related his experience this way:

"A plague of flies during [my internship] provided few places for rest when outside, and howling NW winds became my friend. While on shark-watch, I would stand in the brunt of a gale, and watch flies launch out towards me from the protected south wall of the lighthouse, only to be immediately caught in the high winds and vanish. Standing there with a fly swatter I could kill 20 at a time, only to have 20 more instantly begin to feed on the smashed bodies of their cousins, which I would then swat again. But there was no end to this game... Scoping from behind the carpenter shop was perhaps worse still. Clothing had to cover EVERY bit of skin to avoid insanity. Only a small hole in your hood to view the eyepiece was possible. Afterward, your clothing was peppered in tiny fly turds, innocent enough until you contemplated the sheer number of them"

With a list of numerous unanswered questions, we look forward to delving deeper into researching these little buggers. Until then, though, we are simply trying to avoid being carted off the island in straitjackets. And we are extremely hopeful that our next blog will be about the swarm of birds that descended upon the island and devoured every last Corm Fly.

                         Here's a look at what we really mean by Covered in Flies.