Saturday, September 14, 2013

Into the Cage–Banding Milano Negro in Spain

Welcome to my second post covering my recent trip to Tarifa Spain for the Idaho Bird Observatory to study avian migration with Fundación Migres. You can learn about the purpose of my trip by reading my first blog post titled Migration on an Unimaginable Scale.

On two occasions during my trip we banded Milano Negro (Black Kite - Milvus migrans). This highly migratory species travels from Europe down across the Strait of Gilbralter and into Africa for the non-breeding season. These birds rely on thermals which form over land due to the uneven warming of the earths surface. These rising columns of air, help the bird gain altitude before attempting the 10 mile crossing into Africa. Thermals do not form over water, so migrating birds must use powered flight to make the crossing. If the weather isn’t just right, they will wait in the fields near Tarifa for the weather to change. Each day hundreds more arrive and fill the fields. This is an excellent time to “band” (or “ring” if you are from Europe) these migrants as there are many present and there is little migration counting to be performed.

Milano Negro (Spanish) or Black Kite (English)

A large cage is first baited with bones and scraps from a local butcher shop. The Milanos are scavengers and are attracted to the “aged” meat. Hours usually pass before the first bird enters the cage. Once the first bird enters, it is not long before more show up. The numbers balloon quickly as hundred of birds show up, attracted by the action. The trigger is pulled and the birds are trapped. We captured 99 Milanos in one event, with hundreds more perched on the cage and on the ground around the cage.

99 Milanos in the cage.

Then came the very exciting and challenging job of extracting the birds from the cage. One may question the sanity of voluntarily walking into a cage with 99 free flying raptors. Body armor was not available! It’s a good thing the birds are fairly non-aggressive. If these were Red-tailed Hawks I would not have come out alive! The Milanos just droop their heads once they are picked up.

Juvenile Milano not putting up a fight.

The birds are placed into breathable bags and their legs tied to keep them secure. Once in the bags, the birds relax further and stay quite calm. The weather remained hostile for crossing the Strait so we weren’t delaying their journey and they should have gotten a good meal while in the cage.

Milanos ready for processing.

The birds are banded, measured and prepared for release. However, 19 lucky individuals were selected to help advance our scientific knowledge of migration by carrying a temporary backpack which contains a GPS unit and a cell phone text message component to transmit it location to the researcher on a regular basis.

GPS units with text messaging capability.

The researcher from Portugal is studying the flocking behavior of migratory birds. These GPS units will help him to determine to what degree these birds stick together. It will also help those of us studying migration at the Strait to understand the weather conditions under which they crossed, the time it took to cross, etc. It is tremendously valuable information.

GPS Backpack on a Milano.

The units are attached with harnesses which biodegrade under ultraviolet light. Within 3 months, the string will break, immediately releasing all four corners and freeing the bird of its obligation.

The experience exposed me to a new trapping technique used with scavenger birds, allowed me to practice the European measurements which are taken differently than in the US, and enabled me to spend time with the researchers discussing migration and flocking behavior. It was a fantastic experience.

Adult Milano ready to go to Africa!

Check back later for more information on my trip!

Thursday, September 05, 2013

Migration on an Unimaginable Scale

After leaving my 21 year career with Hewlett-Packard in 2009, I have spent my life in school getting two more degrees and one certificate (B.S. in Biology with an Emphasis in Ecology, M.S. in Raptor Biology, and a Graduate Certificate in Geospatial Information Analysis). During this time I have conducted research in two primary areas, publishing papers in both. The first area was the core theme of my graduate thesis, Northern Goshawk (Accipiter gentilis) Breeding Ecology. The second area is focused on avian migration. My work in this later area opened up a tremendous opportunity which I have just recently participated and is the topic of this post.

Most of my work is conducted as an employee and/or volunteer with the Idaho Bird Observatory (IBO). IBO is an "non-profit academic research and community outreach program of Boise State University focused on impacting human lives and contributing to conservation through a combination of research, education, and community engagement". My role is primarily in the research aspect of this mission, although I do also participate in outreach and education. I perform fieldwork, design projects, analyze data, and publish results. For some projects I am paid, for others I am not. Regardless, I love the birds and I love the work.

The IBO organization had received money from a grant to send students to Spain to study avian migration at the Strait of Gilbralter. I was lucky enough to be chosen for the trip. The last two weeks I have worked for Fundación Migres in southern Spain counting migrating raptors, banding Black Kites, banding Barn Swallows, and counting migrating seabirds. I met committed scientists, learned a tremendous amount, saw 47 new life birds, and enjoyed fabulous Spanish food and culture. It was a spectacular experience. This is the first of a series of posts highlighting my trip.

Cigüeña Blanca (White Stork - Ciconia ciconia) migrating to Africa.

The Strait of Gilbralter is one of three main sites where long-distance migrating raptors pass from Europe into Africa. Most of the birds in western Europe migrate down through Spain to the Strait where the crossing is only 14 km to Morocco. Some birds travel down Italy and island hop across the Mediterranean, while most eastern European birds travel through the middle east. Fundación Migres currently maintains two "count sites" for migrating raptors and storks near Tarifa for monitoring population trends, phenology changes, and the general ecology of migrating birds. I spent the majority of my time in Spain counting migrating birds at these two sites.

Map of the Strait Of Gilbralter. Count sites near Tarifa and near Algeciras.

Mount Sidi Moussa (Morocco) as viewed from Spain (14 km).

Each day one or two biologists are assigned to each count site to count all migrating raptors from 9:30am until 5:30pm. Each bird that is spotted must be identified and tracked to see if its flight direction is consistent with a migratory bird. With multiple mixed flocks in the sky at once, it can get fairly hectic. Of course, we do miss birds. There is no way to spot every one. We also likely count birds which don't end up crossing the strait. The point is to have a consistent effort and protocol so that the numbers we do collect can be a consistent index of the number of birds actually migrating. Since these site are excellent places to observe birds, many tourists also show up to watch the migration.

The work is both physically and mentally demanding. While there is a great deal of sitting involved, the strain on your neck (from looking up), on your arms (holding up binoculars), and on your eyes (staring through binoculars into bright sky) definitely takes its toll. It is mentally straining to stay focused for that length of time, often shuffling counts of up to 4 species at a time in your head. A single flock can contain hundreds or even thousands of birds (2300 White Storks was the biggest I saw). We used handheld counters to track counts of multiple species when things got busy.

Andres counting with 4 species counter.

Cazalla count site.

Algorrobo count site.

There are a number of challenges facing birds crossing the strait. It is not just the distance, the lack of thermals and wind make this a very challenging portion of their migration. Many raptors depend on thermals, or rising columns of air, to gain altitude. Thermals are generated by the uneven warming of air over land. They do not occur over water. Thus migrating raptors must use flapping power to maintain altitude when crossing water. This is easier for some raptors than others. Wind is the other challenge. A tail wind may help with the distance, but it also decreases the lift generated by a birds wing. A head wind, while enabling more lift, can decrease speed and thus increase the effort required. A strong east wind, a "Levante wind", can blow a bird off course into the open ocean. Unlike waterbirds, raptors are not able to land on water to rest, if they land, they die. The most challenging crossing conditions occur in a Levante wind, which unfortunately for the birds are common in autumn.

Abejero (Honey Buzzard - Pernis apivorus) uses natural flapping style of flight to easily cross the strait, even in difficult conditions.

Species which do not have a natural flapping style and are heavily dependent upon thermals, often must wait for the weather to improve before crossing. This can require days of waiting for the right conditions to cross. Each day, more and more migrants arrive in the fields around Tarifa waiting for the weather to change. Hundreds, even thousands of birds waiting. When the wind shifts, they leave en-masse. My first count day in Tarifa was one such day - 4400 Black Kites and 4300 White Storks made the crossing that day! Our count for the day? Over 9000 birds!

Milano Negro (Black Kite - Milvus migrans).

Black Kites "thermalling" up before crossing.

Cigüeña Blanca (White Stork - Ciconia ciconia) preparing to cross.

The spectacle of thousands of birds per day approaching the strait to cross is humbling. So much life, so much biomass, it seems inconceivable that this many animals exist. When the the Abejero (Honey Buzzard) started migrating we were counting over 3000 birds per day. The day after I left - over 20,000 Honey Buzzards! Unbelievable.

Alimoche (Egyptian Vulture - Neophron percnopterus).

Why study migration? Birds are a very important part of our natural and now human influenced ecosystems. A good portion of birds on the planet, over 40%, migrate on an annual basis. As the planet changes, so does the influence on individual bird species. A migratory bird faces new challenges in each stage of its annual life-cycle. Some are threatened on their breeding grounds, some on their wintering grounds, and nearly all on the journey in-between. Studying bird migration can provide early and relatively inexpensive insight into the trends within migratory species. This knowledge can better inform conservation measures before trends become too catastrophic.

Calzada - (Booted Eagle - Hieraaetus pennatus).

Fundación Migres now has a long-term dataset to investigate the trends in European long-distance migration. My role in all of this is to add to their published literature by creating a new research project analyzing their data and co-authoring a manuscript with them. We have chosen a preliminary topic and the work has begun. It should keep me busy through this fall. This is why I left my previous career - to spend time in the field, to analyze and publish results, and to positively impact the conservation of species on this planet. This is just the latest opportunity I have been given.

Culebrera (Short-toed Eagle - Circaetus gallicus).

The Fundación Migres team is a group of fantastic people. They are gracious hosts, they are incredibly knowledgeable, they taught me a great deal, and I now consider each one of them my friend. I hope I have the opportunity to return next year!

I will post more summaries in the coming days - Black Kite banding, Barn Swallow banding, seabird migration, and one on food and culture.