Bald Eagle Update

Ray Brown, Refuge Biologist
8/1/06

Eagle Update - 8/1/06 - Bombay Hook's Eagle nest produced one fledgling this year.  The bird fledged between June 14 and June 20, 2006.  The young seemed large and strong and had been branching out in the nest tree for weeks.

        We had high hopes that Bombay Hook’s eagle pair was finally going to nest successfully last year after an eight year long series of failed nesting attempts.  The last year that eagles nested successfully on the refuge was 1997, when one eaglet was produced.
       
        In 2005, eagles again appeared to be setting up residence at the previous year’s nest deep in the woods on the west side of Shearness Pool.  The birds were seen at the nest a number of times early in the year and were exhibiting a moderate degree of territoriality and fidelity to the nest site.  We were hopeful that the pair had produced one or more eggs but we were not able to confirm it.  When the time came for the eggs, if present, to have hatched, the eagles apparently abandoned the nest and have not been seen there since.

        In the winter of 2005-6, activity at the nest seemed to be increasing again, based on the presence of fresh whitewash (excrement) found under the nest tree and adjacent trees, and the presence of prey remains in the area.  However, no eagles were seen at the nest site so it appeared that birds were again only making a half-hearted attempt at nesting.

        Then on the weekend of January 28-29, two refuge visitors separately reported seeing a large nest with an adult bald eagle near the Allee House.  Other visitors may have seen the nest earlier but did not report it.  Refuge staff located the nest on January 30 and have observed one or two adult bald eagles regularly associated with the nest since that time.

        This time the eagles seem to be more intent on nesting than in recent years.  In early February, an eagle was observed sitting in the nest in an incubation posture, spawning speculation that the female had laid at least one egg in the nest.  From then until mid-March, the eagle pair took turns sitting in the nest, presumably incubating one or more eggs.  The suspected “due date” for the first of these eggs, if indeed there were any present, was around the Ides of March.

        On March 17, an adult bald eagle was observed standing in the nest, intently staring at something in the nest.  Soon the other member of the pair arrived, and both eagles stood in the nest staring at some apparently new object in the nest that intrigued them.  Could it be that an egg was hatching or that an eaglet had recently hatched out?

        On March 22, an adult eagle was observed delivering two different prey items to the nest 40 minutes apart, while its mate remained in the nest.  One of the prey items was a fish, but the other one could not be identified because of the distance of the observer from the nest (over 2300 feet!).  The eagle in the nest proceeded to tear at the prey items, turning its head to the side every now and then as if feeding a small eaglet down in the nest.  Could it be that the refuge’s eagle pair has successfully produced young after so many years of failure?

        Even if eaglets are in the nest, they’re not out of the woods yet, so to speak.  Eagles in Delaware have experienced a slower recovery than eagles in other parts of the country, leading to speculation that persistent pesticides and other contaminants produced and used in the Delaware River watershed in the last century may still be affecting the reproductive success of these majestic birds.  Eaglets also fall prey to various avian and mammalian predators, such as raccoons, hawks, owls, and crows, or may starve because of an insufficient prey base or inattentive parents.

        Nest failure by eagles also can often be attributed to human disturbance near the nest.  Individual eagle pairs have their own tolerance limits when it comes to human or equipment presence near the nest.  For example, some eagles have nested successfully for years near major highways or developments, whereas other eagles have abandoned their nests when a construction or timber harvest project has occurred near the nest.  Bombay Hook’s eagle pair has demonstrated to be intolerant of human presence near the nest, often flushing when humans have come within sight of the nest tree, even long distances away.  The eagles’ intolerance for human presence near their nest is the reason that Parsons Point Trail is typically closed during the nesting season—to keep visitors away from the historic nest location on Shearness Pool.  The refuge will be undertaking additional management modifications (including area closures) and monitoring activities to ensure that the eagle pair has the greatest probability of nest success this year.

        The eagle nest can be viewed best from two locations along Dutch Neck Road.  The first viewing location is directly in front of the Allee House.  The nest is about 2100 feet south-southeast of this location.  The second viewing location is about 0.25 mile east of the yellow gate by the Allee House.  The nest is about 2350 feet south-south west of that location.  Posts have been erected at this location to aid in sighting in on the nest.  The eagles have not yet shown signs of being disturbed by single observers or small groups at either location.  The nest can be seen with the naked eye from either location, but a spotting scope is needed to observe eagle activities at the nest.  Nest observations are best made early in the morning before the sun heats the air and causes too much distortion.

        The area around the eagle nest has been closed to visitors to prevent disturbance to the eagles and to afford the eagles with the greatest opportunity to successfully raise young this year.  We also ask that persons and groups viewing the nest remain respectful of the eagles and try to minimize their visual and audible disturbance in the area.  Remember that even though the nest is over one-third mile from either viewing location, the eagles can still see people and vehicles at either location, and can hear loud noises from those locations if the wind is right.

        To help keep track of the status of the nest, we will be installing an eagle observation record box at one of the viewing locations mentioned above.  You can help us monitor the progress of the nest through the nesting season by writing down your observations on the datasheets on the clipboard inside the box.  We expect that eaglets will be confined to the nest until at least the early May, at which point they should start to “branch out” in the nest tree in preparation for fledging.  The young eagles are expected to leave the nest tree and take their first flight some time in the first two weeks of June.  The immature and adult birds should remain in the general area around the nest for about two months after fledging, as the parents still feed the young during that time.  After that, the young will probably disperse from the area.

References:

Buehler, D. A. 2000. Bald Eagle (Haliaeetus leucocephalus). In The Birds of North America, No. 506 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

Cline, K.  1985.  Bald Eagles in the Chesapeake: A Management Guide for Landowners.  National Wildlife Federation, Washington, DC. 16 pp.