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!