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How to Set Up a Bald Eagle Census

Bald Eagle Biology

Guide Lines for Establishing a Meaningful Wildlife Count:

1. SET OBJECTIVES

The objective for most counts by naturalist groups is to show:

----- Regional changes in the species numbers over years

----- Seldom are we measuring absolute changes in numbers since there
are usually so many variables that are not practically controlled.

-----

2. BE CONSISTENT:

----- Choose confined period (1 week of May??) each year.

----- Keep the counting stations at consistent locations.

----- Keep the counting techniques, time allotted etc. consistent.

----- Keep the same or as many of the same counters each year.

For more detailed instructions see more: ...........
 

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To Feed or Not to Feed Eagles

Bald Eagle Biology

To Feed or Not To Feed Eagles?  A Review
=============================================

Many conservation organizations and governments not just support feeding wildlife but depend upon the funds raised from selling bird food or the taxes generated.  Feeding wild birds is big business.  It is also a practical business.   Undoubtedly the only way our degraded city or urban habitats,  with their natural grasses, shrubs and trees  replaced by roads,  houses and gardens,  can house any wildlife, and particularly birds,  is for humans to replace some of the items we have destroyed.  The artificial garden plants don't always produce the same seeds, pollens or insects that feed our native birds.   

The  human supplemental feeding of these birds with bought seeds, suet and honey-water  etc. provides many native species with the key items destroyed and missing in the urban environment  -- the food items that were removed by human development.  Of course some feeders also attract sharp-shinned and coopers hawks, merlins and peregrine falcons, assisting other elements  in the food chain indirectly.

That feeding wildlife is a generally accepted principle and   ..........

 

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Bald Eagle Annual Cycle

Bald Eagle Biology

The Season of the Bald Eagle in Southern BC       Update:   Jan 2009

Egg laying:

    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

Incubation:
    

    Starts with laying of 1st egg.

Hatching:

    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:

    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.

Post Fledging:


    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.

Nest Building:


    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.


 SPECIAL REQUEST:

    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.

David Hancock
Eagle Biologist.
Hancock Wildlife Foundation
 

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Mating Behavior

Bald Eagle BiologyMATING BEHAVIOR:

Bald eagles mate from the time of returning to the nest territory in early fall through egg laying, and sometimes a few months after. Like all raptors that I know, the mating takes place when the female is securely standing on a perch, usually a high tree limb, and the males gently lands upon her back, using both his wings to carefully balance, and then curling his tail and cloaca under the female’s tail, which she has simultaneously moved to the side as she turned her cloaca upwards so the two cloaca touch face to face. The sperm passes from his cloaca to hers and then travels up the oviduct to meet the downward flowing ova for the ‘meeting’, the fertilization.

What great moments of trust. These great predators who can instantly kill prey with the sharp and powerful talons are now, so gently and trustfully, coming in direct contact. The trust that allows the female to accept the male's killing talons onto her vulnerable back is quite extraordinary – but it is an essential and ultimate act of the bonding that has been developed between them. No bonding, no trust, no mating, no young, no species!

Lets go back: The Pre-nuptials!!

On October 9, 2002 1030: I was at our Blaine, WA warehouse and heard an adult bald eagle scream – I immediately ran outside as this was the first record of the eagles return since their departure in mid-July when they left the nearby nest with the young. But the intensity and pitch of the call was most unusual. It was the male's higher pitch but the intensity and constancy of the calling was unusual. But I could see no other birds around or direction to his intentions. This was their favorite hunting perch overlooking Semiahmoo Bay so I was used to them being here.

The male continued his calls almost non-stop for over an hour when all of a sudden he changed the pitch and intensity – something was up and I darted outside to see what. He was now standing horizontally on the branch, his head stretched outward to the southern shore of the Bay and his calls were quick and loud. Within a few seconds later and I could focus on the source of his calls – another approaching adult eagle – headed straight at us. The approaching bird stared to scream and it was obviously a female by the deeper call, she circled the calling male and landed on the adjacent tree about 80 feet away. Both birds kept up the calling, and within a few seconds it developed into a “unison” call, with both birds doing the same thing at the same time. Each bird arched its head forward and then upward and backwards over it's shoulders so the head followed about a 180 degree arch – all the time calling in unison. .

I was mesmerized. I had seen this intense behavior before but always later in the year and as a prelude to mating. Within a minute of these unison calls the male took off, flew directly to the female's tree and lighted beside her. Here they continued, even increased the intensity of the calls and head throwing, always in absolute unison. Then it happened. The male jumped up on the female's back and they mated. This was October 9. This was approximately 5 months from her first egg. What was the explanation?

I believe I just witnessed the return of the pair to their nesting territory from the short ten week fall northern migration. But what a reunion, what a reaffirmation with incredible vocal intensity, all taking place on their two favorite hunting perches, and then the ultimate, mating. What a climax to the event.

We know that eagles build and intensify the mutual bond between the pair through aerial displays, and particularly through the described mutual vocalizations and displays. But what I think I witnessed that day was the actual moment of their arrival back at the nesting territory after their separate northern sojourns at the end of the last breeding season, their re-confirmation of the bond, their reconfirmation of each other. In 55 years of eagle watching I have seen a lot of eagle courtship, all the aerial flights, the mutual calling and many matings. But never have I seen it done so intensely, and never so early in the year.

Just 40 miles south of Blaine WA, on the Skagit River, the USF&WS had banded a pair of adult eagles with solar powered satellite tracking devices. Sadly their two young were not tagged. But the story of the adults northern migration was quite astounding. The normal pattern of fledging occurred. The adults quit feeding the eaglets in the nest, after about 3 - 5 days they get hungry and make their first flight with the concerned parents watching. After another week of flying around the nest territory, sometimes picking up food that the adults have been eating nearby, the adults simply fly off and leave the youngsters to their own fate. Harsh but obviously successful.

But this story is about what happened next to the adults. The male, now being tracked by his satellite ..... >

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Age of a Bald Eagle Nest

Bald Eagle Biology

Bald Eagle Nest: Probably pushing 100 years old -- PLUS!

Between 1963 and 1967 a bald eagle nest in my Barkley Sound Vancouver Island study area was annually used and produced 1 or 2 young each year. This leaning cedar tree was probably in excess of 300 years of age. The nest was very old from many years of constant use. I had climbed to the nest in the 1960's and my notes state it was a very old nest, “well weathered and lived in”.Size, 6 feet 2 inches across and about 2.5 feet deep. The nest had probably been occupied the previous 30 - 50 years.

This nest was one of 136 occupied territories in that part of Barkley Sound that I studied.


Another Visit in 2003


In July of 2003 my wife, daughter and I were kayaking in Barkley Sound and as we rounded the southern end of this same Island I stated how in the early days my favorite nest was suspended over the water in a leaning cedar tree. We rounded the bend and there was the same leaning cedar – with two large full grown young standing in the nest.

As an update to the above. Barkley Sound was largely logged prior to the 1950's and by the 1970's was designated part of the West Coast Regional National Park. During my study period in the mid 1960's we never saw more than 1 kayak or canoe party per summer and perhaps 3 to 5 pleasure boats. Commercial salmon trollers and shrimp trawlers were constantly working the Imperial Eagle Channel. Today the adjacent area houses numerous trailer parks and campsites, boat launch ramps and an incredible armada of kayaks, canoes and pleasure boats. And the area seemed to have as many bald eagles as it did 40 years ago. Not all is lost.

A question comes to mind: Will a tree sustain an eagles nest for two or three hundred years? Certainly the trees can live twice that long. And how many different adult eagles nested in this single location?


David Hancock
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