Bald Eagle Annual Cycle
Wednesday, January 21 2009 @ 07:14 PM EST
Contributed by: davidh
The Season of the Bald Eagle in Southern BC Update: Jan 2009
Egg laying starts the last week of February and goes through March. Some re-laying in nests where eggs are lost will continue into April.
Peak laying:: March 10 - 15
Starts with laying of 1st egg.
First of April through April for first nest or first clutches. If a nest is lost approaching egg laying time this can delay onset of laying. I have seen 4 nests destroyed (all fell out of tree due to inferior branch support) and then adults built 5th nest on suitable cross-limb and succeeded in raising young -- that fledged in late Sept.
Fledging takes place on the 12th week. In some of the urban areas where there are fewer 'secure' nearby feeding perches the adults seem to be using the nest to feed the full grown young "after" they should have been fledged. This prolongs the chicks staying in the nest and delays the abandoning action. This has resulted in some urban nests having the chicks still present for 13 - 14 weeks – or even a longer time.
This is the period when the young have fledged but are still flying around the nest territory. This period is usually only 3-8 days before the adults abandon the chicks and the parents both leave. In the urban areas, as implied above, this process is sometimes being delayed as the chicks keep getting fed in the nest after the 12 weeks while in the wilderness situation the parents would not normally bring food into the nest after fledging. In the more wilderness areas we very seldom saw adults bring food to the nest site. On occasion the adults would be feeding 1/4 mile or so from the nest and the young would see them, make aggressive attacks to take the food with the parents simply backing off. There was never ‘training to hunt activity by the parents’.
After the abandonment by the parents the young would spend another 4 – 6 days in the nest territory, frequently calling, and then they would be gone. In the urban setting we are again seeing both parents and young stay around the nesting territory for longer periods and in a few instances we believe that the adults may not even leave the general area.
Migration / Dispersal Period:
After leaving the nesting territory both adults and young leave the area. The newly emerging satellite tracking data is suggesting that this dispersal is over a much wider geographical area than we first thought. Most certainly it is generally north to where more food is available early.
Return to Nesting Sites & Territory:
This is happening earlier each year. Generally the adults start to appear about the last week of September through mid October to re-stake claim to their territory. They usually do a little nest rebuilding, maybe some mating and then just hang around to lay claim to the territory. On the outer west coast, a more wilderness area, we did not see a major return of the breeding adults to their territories until mid to late November.
In southern British Columbia the nest building begins seriously in January. If the nest is lost a new nest may be started earlier. The cycle begins afresh.
The Hancock Wildlife Foundation research arm is about to launch a program for coordinating the collection of bald eagle nesting data continent wide. The above time summary for nesting eagles along the southern British Columbia and Washington coasts will serve as a guide in developing a similar time schedule across North America. Towards this end we hope to encourage many of you to record the details of nesting eagles in your area. We will shortly have the entry screens and data base available for our observers to enter their data directly. In the meantime just record on paper your observations.
Much thanks and best regards.
Hancock Wildlife Foundation