August 14, 2006
Heading South
Nest Update: A cam watcher saw a parent today that looked like the father. She said in another shot he was facing more toward the cam and was missing a necklace (brown chest coloring); this would indicate that it is the father. At this point in August, it's very possible that the mother osprey has started migration, since the young birds are very independent these days and seem to need little in the way of food. But we'll keep an eye out for any parents at the nest, to confirm that the mother is gone.
One of our cam watchers recently asked about my reference to the "chicks" and whether this was the correct term for them now. In fact, the young are now "juveniles." I use the term "chicks" as a nickname, much as a human parent would refer to the "kids." But for those wanting to know the correct biological terms, I can offer the following definitions, which were in a paper titled "Names of Age Groups of Young Birds" by Harold Wood:
NESTLING -- A young bird within and not ready to leave the nest.
FLEDGLING -- Normally ready or physically able to leave the nest and survive, and still being cared for by its parents.
JUVENILE -- A young bird out of the nest and able to take care of itself, but which has not completed the post-juvenal molt.
IMMATURE -- A bird after completing the post-juvenal molt, but has not acquired the complete adult plumage.
YOUNG -- A generalized term applied to the bird less than one year old, when a more definite determination of age cannot be made.
Young ospreys only take about eighteen months to acquire their adult plumage, and they do not have multiple feather stages, so with ospreys they are referred to as juveniles and then immatures until they get their adult plumage. Young bald eagles take about four or five years to acquire adult plumage, and during the process they go through several stages of feather development (as their head and tail slowly turn from brown to white), so when speaking of young eagles, biologists break those immature stages down into segments such as Basic I, Basic II, etc. (For a better description of the Basic stages and a look at how the bald eagle's feathers develop, check out this PDF article).
Migration Destination
In this web log I wanted to discuss where our osprey family will likely go when they leave us. Ospreys are one of the best-studied migratory species in North America as over the years many ospreys have been fitted with radio transmitters and tracked on their way down to Central America, South America, and the Caribbean. In addition, many ospreys have been fitted with leg bands and then recovered once they showed up dead in these same areas. So biologists have a good idea as to where mid-Atlantic ospreys go once they leave for migration. We can't say exactly where each of our family members will stop, but we can offer a good hypothetical itinerary.
When an osprey is ready to leave Blackwater Refuge, it will likely strike out toward North Carolina, possibly stopping around Hertford and the Albemarle Sound to do some fishing and refueling. Ospreys stop to eat when migrating, but they also have been seen flying with a fish in their talons, which they munch on while in flight.
While tracking ospreys, biologists have found that some mid-Atlantic ospreys stay over the East Coast mainland while some head out over the Atlantic Ocean and follow the coast. Ospreys are very strong flyers and do not rely on soaring as much as other raptors (such as bald eagles), so ospreys do not mind crossing long stretches of water. (It's interesting to note that European ospreys may cross the Sahara Desert and the Mediterranean Sea).
Once an osprey leaves the Outer Banks area of North Carolina, it will likely head down to Cape Fear, North Carolina, where the Cape serves as a launching point for many ospreys that decide to strike out over the Atlantic Ocean and not regain land again until Florida.
After flying out over the ocean, the osprey might land in the area of the St. Johns River in Florida, which is the longest river in the state and a popular place for ospreys as it offers miles of quality fishing.
The osprey will then head down to the Miami, Florida area where the bird will prepare to cross the Straits of Florida and land in Cuba. Ninety percent of ospreys nesting on the Eastern Seaboard of the U.S. spend time in Cuba, and some even spend their entire winter there. But the majority will continue on to Haiti, and from the Port-au-Prince area, launch out over the Caribbean Sea and land in South America.
Making the 400-mile flight across the Caribbean Sea is the most taxing part of the ospreys' trip, so most birds stop as soon as they hit land (often around the Guajira Peninsula) and spend time resting and fishing. Some ospreys go no farther, while others fan out all over South America, with some going very deep into the continent. (On this map, look for the little houses to see some known destinations for migrating ospreys.) It's been reported that females tend to go farther south than the males, which might have something to do with the females' larger size. For those ospreys that travel inland, they will often hang around large rivers including the Amazon and the Orinoco River.
Ospreys will likely roam around their home area throughout the winter season, but most birds stay in the same general region until they are ready to head north again. Adult birds will start north in the following January, February or March; but juvenile birds will stay down south for an extra year before returning north. Ospreys are as loyal to their chosen wintering grounds as they are to their breeding grounds and will normally return to the same southern region each year.
Threats to Ospreys
One of the sad facts of life is that ospreys face many threats on their journey south -- a journey that could reach a length of 2000-4000 miles and take from 15-50+ days to complete. Common causes of death among migrating ospreys include electrocution; collisions with power lines, buildings, cars, and cell phone towers; storms; starvation (either from lack of fish, water pollution, or lack of fishing skills); drowning (from fishing lines); pesticides; and shooting.
In Latin America and the Caribbean countries, shooting is a major cause of death for ospreys. Many farmers in these regions consider all raptors to be a threat to their livestock, and so they shoot most birds of prey. But the main reason for shooting is that ospreys frequently hunt for meals at fish farms. Fish farming is a growing industry in Latin America and the Caribbean countries, and ospreys often use the farms for an easy meal, which frequently leads to the ospreys' death.
The U.S. Fish and Wildlife Service has funded a program called "Wildlife Without Borders" that has researched the problem of osprey shootings at fish farms. The research indicates that as many as 14,000 ospreys are killed by fish farmers each year within the seven Latin American countries surveyed. When the research is applied to the twenty-one Latin American and Caribbean countries that have fish farms along the ospreys' migratory route, the actual mortality rate for ospreys is probably much higher. In fact, one farmer surveyed admitted to shooting about 200 ospreys each year.
The USFWS report that, "farm owners spend millions of pesos each year trying a variety of bird deterrents such as noise-making devices, scarecrows, dogs and hired-man patrols. None of these methods has proven to be effective." Some farmers have reported success using lines of nylon twine, as well as nets to keep the ospreys away from the fish. The USFWS reports that many farmers seem genuinely interested in finding ways to protect the ospreys, and the researchers hope to continue working with the farmers to find better and more affordable solutions. You can read more about the USFWS' research efforts on their International Affairs page.
Meanwhile environmental groups are also working to educate farmers and citizens in an effort to decrease shootings and to increase appreciation for ospreys throughout Latin America and the Caribbean countries. National Geographic News published an interesting article about the growing enthusiasm for osprey protection in Cuba, which is THE major hub for migratory ospreys from the East Coast, and hopefully this trend will continue.
The difficulties that ospreys face during migration season serve as a reminder to humans that wildlife protection is often an international affair. Ospreys know nothing of human economies, artificial borders, international law, or shifting politics. The osprey sees the world as "home" and moves about as if it is welcome everywhere. We hope that one day the osprey truly will be.
Until next time,
Lisa - webmaster
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