The Delaware Valley Eagle Alliance announces the successful
fledging of four bald eagle chicks from a nest along the
Delaware River in Northampton County, PA.
Directors, John and Yoke DiGiorgio began recording their
observations and documenting, through photography and
documentary film, starting the first week in April 2009. The first
chick was observed that first week in April. The fourth chick
was observed and documented on April 27, 2009. PA Game
Commission was notified and provided with documentary film
confirming the historic event.
Clutch size in bald eagles generally varies between 1 and 3,
with 2 being the most common. Reports in the literature of 4-
egg clutches are very rare, with some suggesting that they
result from two females laying eggs in the same nest. In
1986 on the Chesapeake Bay, a 4-egg clutch was successful
with no sign of an extra female. An account was never
published.
The DiGiorgios have completed capturing fourteen weeks of
footage documenting this historic event, from the time that the
4 chicks were first observed through several weeks after they
fledged (first flight).
John DiGiorgio stated that, based on when we first observed
the appearance of each of the chicks, we estimated that there
was a one and a half to two week age difference between the
oldest chick and the youngest chick. Chick #1 was visibly
larger and more developed than the younger three and chick
#4 was visibly smaller and less developed than the older
three. This remained the case up until they fledged.
Feeding this 4-chick brood was a time consuming activity and
involved both adults. DiGiorgio recalls filming on a particular
evening in May where, over a two and a half hour time span,
the adults brought in a total of five fish and fed the chicks
continuously. The chicks formed a semi circle around the
adult and were each fed a small portion of the fish at a time.
The adult would then move to the next chick, and the next,
and the next and return to the first to start again. The adults
did not appear to favor one chick over another. All were fed,
even the youngest. Very little aggressive behavior between
the chicks was observed prior to fledging, even during
feeding. Fledging occurred during the 3rd week in June with
chick #1 fledgling first, chicks #2 and #3 fledgling two days
later and finally chick #4 three days after that.
A documentary film is being developed, with the plan to
premier it during EagleFest 2010 (scheduled for Saturday,
January 16, 2010 in Narrowsburg, New York), an annual
event that the DiGiorgios founded and organize.
The DiGiorgios are also collaborating with Dr Bryan Watts,
Director, Center for Conservation Biology to co-author a
research paper that documents this rare event. The paper
will present an account of this nesting event in the context of
current thought regarding limitations on clutch and brood size
in bald eagles. Dr. Watts has monitored more than 6,000
nesting attempts by bald eagles and has never recorded a 4-
chick brood. He states that "it is truly incredible for such an
exceedingly rare event to be so well documented".
