July 27, 2006
Eagles & Ospreys
Nest Update: At this point, we're still looking for signs that our fourth chick is safe. We haven't seen any definite indications of his presence other than the dark photo from Sunday, and we can't be sure that was him. So at this juncture, we just don't know what to think.
Since the older chicks first fledged, we haven't seen a lot of the father osprey either, so there is a possibility that the father is off somewhere keeping an eye on the missing chick. But it is very odd that while the two older fledglings often return to the nest -- to eat, preen, and rest -- the other older fledgling is no where to be seen.
Some cam watchers have asked about what types of threats there are around the Refuge. Blackwater Refuge is in a pretty safe area for ospreys, but there are still risks. Sometimes young ospreys get electrocuted on power lines, drown while learning to fish (by getting caught in fishing line) or hurt themselves while learning to land. As for avian threats, Great horned owls and bald eagles have on rare occasions been known to take out a full-grown osprey, but they would more likely prey on eggs and small chicks.
Another cam watcher asked if our missing chick could have taken up residence at another osprey nest. Young ospreys do visit other nests (we had a fledgling visitor this week) but they do not normally stay at the other nest. Biologists have speculated that a "runt" might possibly spend more time at a neighboring nest because the littlest cannot get enough food at home, but our missing fledgling was one of the bigger birds, and would not have had trouble getting fed by the parents.
So at this point, we will just hope that the missing bird is all right and is with the father somewhere. Perhaps once the mother migrates in August, the father and missing chick will be seen more at the nest, as the father will then be in charge of protecting all the fledglings until they are ready to migrate.
Our youngest chick appeared to take a flight on Wednesday morning. He had been flapping quite a bit and finally seemed to disappear from the camera view for several minutes. He will be nine weeks old on Friday, so we're marking his fledging at 61 days -- which was about the same as our youngest last year. Despite his apparent flight, the youngest is still spending a good bit of time in the nest.
Meanwhile our two older fledglings have been seen bringing in their own fish. We're not sure if they're catching the fish themselves, or if the father or mother are providing the meals off-camera, but the young have been bringing them on a regular basis. Sometimes the mother lets them "hog" the fish, and sometimes she takes it away and feeds it to the family, or eats it herself.
Contest
I emailed our Blackwater staff and asked them to pick up the pace on the contest results. I know they're having a hard time deciding, but I asked if they could give us an answer soon. I'll announce the results as soon as I get them.
Eagles and Ospreys
It's hard to talk extensively about ospreys without mentioning their main nemesis -- the bald eagle. Eagles and ospreys have a unique, combative relationship that is sometimes visible in the skies over Blackwater Refuge.
Bald eagles may be the national symbol of the United States, but they have not been without their critics. In 1782, during the debate over the choice of America's national symbol, founding father Benjamin Franklin was reported to have said about the bald eagle: "He is a bird of bad moral character. He does not get his living honestly. You may have seen him perched on some dead tree near the river, where, too lazy to fish for himself, he watches the labour of the fishing hawk (osprey); and when that diligent bird has at length taken a fish, and is bearing it to his nest for the support of his mate and young ones, the bald eagle pursues him and takes it from him." Franklin went on to call the eagle a thief and a scavenger, because sometimes the eagle prefers to steal a meal rather than catch one itself.
And that brings us to the osprey: The osprey is known as perhaps the most skilled angler in the natural world. And fortunately for the eagle, the osprey happens to specialize in catching the eagle's favorite food -- fish.
But it gets even better for the eagle, because while the osprey is an agile and powerful flier, it is also smaller than the eagle. The osprey has a wingspan of 4.5 to 6 feet, while the eagle's wingspan can be as much as 7.5 to 8 feet. So a single eagle can dominate a single osprey in most aerial battles.
Ed Schulz, a photographer who has worked with the U.S. Geological Survey in Washington state, was kind enough to lend me a photo that shows perhaps the best example I've seen of the size comparison between the eagle and osprey. In this photo the eagle is practically on top of the osprey as it attempts to bully the smaller raptor into dropping its meal. Ed reports that this photo was part of a series, "where the male osprey was in the process of delivering the headless Pile Perch to the female at the nest when the eagle intercepted them. The female joined in the battle to defend her meal but the eagle did eventually get the fish."
In most battles of this kind, the eagle will prevail by harassing the osprey to the point that the smaller raptor drops the fish just to get the eagle to leave it alone (see photo), after which the eagle will retrieve the meal. But if the osprey is determined to keep its bounty, the eagle will sometimes resort to a physical attack in order to win the prize. Oddly enough some biologists speculate that in the end, the eagle may spend more energy on stealing the meal than it would have used in catching the fish itself.
In the wonderful book, The Bald Eagle: Haunts and Habits of a Wilderness Monarch, one of the authors describes an eagle/osprey encounter on a Saskatchewan, Canada lake that shows how far an eagle will go to get what it wants:
"The eagle attacked from a few feet above and to one side of the Osprey -- once, twice, and then a third time. On each pass the Osprey visibly flinched, for the eagle's talons barely cleared its back. We anxiously awaited the outcome. Many observers had described how typically the Osprey drops its fish, and with surprising agility the Bald Eagle snatches the fallen prey in midair. We were not prepared for what happened. After three unsuccessful attacks, the eagle turned to brute force. This time coming up fast from behind and below, the eagle flipped onto its back, thrust its talons upward, and ripped the fish right out of the Osprey's grasp. What a sight! After quickly righting itself, the eagle turned and flapped leisurely to deposit the booty on its nest."
But at this point, you shouldn't think that ospreys are helpless victims. Although smaller than the eagle, ospreys still have a lot of fight.
As Ed Schulz previously recounted, sometimes an osprey will join up with its mate in an attempt to "save" its meal. Tom Miller, our park ranger at Blackwater Refuge, reports that several times he has seen an osprey head-off an eagle in order to allow its mate to get back to the nest with their fish.
Ospreys have also been known to team-up with their mate to attack an eagle that wanders too close to their home nest. A famous example of this occurred back on July 4, 1996, when former President Bill Clinton released a rehabilitated bald eagle named Freedom on the Patuxent River near the Chesapeake Bay. Craig Koppie -- Blackwater's friendly endangered species specialist -- was the one who helped Clinton release the eagle.
However, what the president and Craig didn't realize was that near the release site was an occupied osprey nest, and when the newly freed eagle flew over it, the ospreys decided to teach the young bird a lesson. The ospreys chased after the poor eagle, pecking and harassing it until it landed in the water where the Coast Guard later retrieved it to make sure it was all right. Eventually the eagle was re-released at a different location that was away from ospreys and other eagles.
At Blackwater Refuge, the bald eagles often fly around or near the Osprey Cam nest, and the ospreys don't react well when they do. The parents will scream at the eagles and chase them away, and normally the eagles will then leave. Once we get near migration, the eagles will begin to circle the platform even more in anticipation of the ospreys vacating it. The eagles like the cam platform because it makes an excellent perch near the river. In the last couple years, we've noticed that we can tell when the last osprey has migrated, because within the next couple days, the eagles are on the platform, indicating that the ospreys are no longer defending it.
So this year, we'll once again look for that first photo showing an eagle on the ospreys' nest, and that will be the most definite sign we'll have that the last osprey chick has headed south for the winter.
Once the ospreys are gone, we will leave the Osprey Cam online throughout the winter so we can watch the eagles and other birds that visit. We get quite a variety of birds during the months when the ospreys are gone, including immature bald eagles, hawks, turkey vultures, Great blue herons and Great horned owls.
General Osprey News
While we're on the subject of ospreys and their relations to other birds, I wanted to share a couple new photos from photographer Russ Yeaton, who photographs a local osprey family at Spring Point Light in South Portland, Maine. In this photo by Russ, you can see the osprey mother is unhappy about a family of ducks that were swimming too close to the osprey nest. And in this photo you can see a gull chasing the osprey as it tries to carry a fish back to the nest. Apparently gulls are thieves, too!
Also, our cam watchers might remember that a while back I posted a photo that Russ took showing a small house sparrow sitting on a twig under the Maine osprey nest. Russ reports that the sparrows do indeed nest in the ospreys' home (in the area where you see the white paper on the nest). Apparently the sparrows are perfectly fine with having a large, powerful raptor as their landlord.
And finally, the nice folks at Public Service New Hampshire emailed us to say that they have an Osprey Cam on their website that features live streaming video of a nest at their Ayer's Island hydroelectric plant in Bristol/New Hampton, New Hampshire. When you visit the site, be sure to check out the interesting Gallery -- and note that the site works best if viewed with Internet Explorer. We're told that the cam nest has two chicks that should fledge in a few weeks. Best of luck to their young ospreys, and to all the ospreys that are making an impressive comeback in New Hampshire.
Until next time,
Lisa - webmaster
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