Monday, July 24, 2006

Still More Questions July 24, 2006

How long will the Cam be on? This is really a question for BRI but I hope the Cam will be on well into August. It partly depends on your continuing observations and the cost. It will be up to BRI to make a decision about the Cam next year. We've alraedy seen a significant drop in the amount of time the fledglings are present at the nest. This is great and as it should be. I suspect that observations near dawn and dusk will provide the best viewing from now on. So keep the observations coming.

Concerning Martha. Someone noted that eagle densities are very high in the Chesapeake area as is food but available territories are limited. This will increase intraspecific competition and lead to injuries and death of some birds. We observed a similar occurrence on Verona Island (near Bucksport) several years ago. The resident male had a blue wing tag (from MA) and one spring three adults showed up at the territory; by nesting time Mr. Blue had dissappeared not to be seen again.

Can adults recognize young from previous years? We doubt it as these birds have undergone multiple molts. I think the only reason the sub-adult was able to approach the nest site recently was that the nestlings had fledged and the adults were not present.

Little getting enough food. We don't need to worry about "Little" anymore; "he" is fine. There is no indication that male fledglings are tended by the male parent, females by the female adult. Doesn't make any long term sense.

Bones etc. I think Mark commented earlier that birds of prey, including eagles, regurgitate pellets composed of undigestible materials such as fur, feathers and bones. When doing food habits' studies we collect these pellets and analyze their contents.

That's all for now. Bucky Owen

Friday, July 21, 2006

July 21, 2006: More questions

There have been several questions about sibling mating and what might prevent it; tough question! In the late 1960's and 70's, when eagle numbers were greatly depressed, there may well have been some interbreeding due to the lack of alternative partners. But that has all changed with literally thousands of immature eagles currently occupying the centeral and northern Atlantic coastlines. Most of our immatures leave Maine their first fall and wander for the next four years, often returning to Maine in the summer months. Others overwinter here when there is an abundant and predicable source of food throughout the winter. For example, here in Orono, at Pushaw Lake, there is a small group of mixed aged eagles that attend the ice fishermen on a daily basis. Anglers regularlly place pickeral and perch on the ice for the eagles. Young eagles are mixing continually during these years and it is unlikely that siblings would encounter each other much during this period except, perhaps, occasionally if they visit their natal area. It is also possible that siblings recognize each other after several years and there is some innate process that discourages interbreeding.

As with most bird species, female eagles select their male partners. With many species, males have established territories and advertise their wares with colorful plumage, displays and song; females then make their choice. Not so with eagles, pairing appears to occur between their 4th and 5th years during times when immature eagles are continously interacting with each other. Recent information, based a great deal on osprey research, suggests that the male then escorts his mate to his natal geographic area. She, in turn, does the final nest tree selection. Theory says that since the male is the prime food provider during the nesting period, he makes the territory choice based on food availablity. Here in Maine we have a great deal of data on former eagle territories and actual nest trees. In the 80's and 90's, as our population grew and new territories were established, we were amazed at the number of old territories that were reoccupied, even 20-40 years after they had been abandoned! Old nest trees, decades after nests had disappeard, were used again. Obviously, there were aspects of these territories that the new male recognized, probably food availability, such as runs of anadromous fish (e.g. alwives). The female, in turn, selected many of the old nest trees that still afforded strong limbs for nest support, easy access and good visibility.

We have limited data on dispersal and nesting locations of our own immatures. One bird Charlie and I banded as a nestling in Ellsworth (Hancock County) ended up breeding along the north shore of New Brunswick. It was 27 years old at its death, the 2nd oldest banded eagle ever recovered! Another breeding eagle we radio-tagged in the Bar Harbor region 15 years ago was banded as a nestling in Michigan and this year, we read the band number of a breeding adult in northen Maine that was banded as a nestling in New York. These are just few examples of the geographic mixing that occurs in our northeastern population. I suspect that it is typical, promotes genetic exchange, and sibling pairing under normal conditions is rare, at best. One last observation highlighting the extent of continental eagle movement was a recording by Mark during his PhD work. He was able to read the band number of an eagle feeding at one of his winter feeding stations in coastal Maine; it was from Saskatchewan!!

Finally, who was that bird seen at the nest on July 15th? I suspect it could have been a former nestling from that nest just checking things out once it was safe to come near. The nest has been productive for the last 14 years so there are a number of immatures out there somewhere. If you check our first eagle image from the 5th of February you will see another visitor. Charlie related to me that he has found several fledglings dead under eagle nests (not their own). There is probably some attraction to all eagle nests for youngsters and if they blunder into some resident adults it may be tough going. Our eagles mate for life and are at or near their territories most of the year. The chances of another individual or pair taking over that site would be very rare. -- Bucky Owen, Unniversity of Maine emeritus

Friday, July 14, 2006

July 14 notes: questions & answers

Greetings all! The two fledglings at the eagle cam' are doing well with flights, getting better at landings, and remain highly attentive to food and adult parents. They also seem willing to pose in front of the camera on a regular basis ... so we continue! You have proven to be dedicated and attentive observers. Your blogs have greatly simplified my job by sharing insights with each other.

The blog has become part of our daily routine to see how things are going and helps us draft the Journal notes! Bucky and Mark are away this week, so I will use the opportunity to briefly address some of the topics you have raised in the last week.

(1) Size differences: Females eagles are about 10 - 15% bigger than males from the same area. Eagles from northern latitudes are larger than those from southern areas. (Thus, a large female eagle from Florida might be about the same size or a bit smaller than a male eagle from Nova Scotia and much smaller than a female from northern regions.) When we handle an eagle, we measure the width of the lower leg and the depth of the beak as reliable distinctions between males and females! When eaglets fledge, they are essentially full grown although there may some of the larger flight feathers are still actively growing when they first take flight.

(2) Identifying Big & Little: When you see the fledglings one at a time, it's hard to judge size and identify them. BRI is controlling the camera zoom, and changes will affect the image size on your screen. Also, relative positions from the camera affect size perceptions. The nest is about 4 feet in diameter and the camera view usually captures lateral limbs about 5 feet closer and further away than the nest. Many have reported behavioral distinctions and quirks between Big & Little: good strategy! Perhaps next year we will band the eaglets (when about 6 weeks old) and use color bands with distinct codes to aid your viewing. You will be amazed that such an intrusion at the nest is tolerated, but careful timing is the key safeguard ... as it is in most of our management decisions to avoid disturbances to breeding eagles.

3) Little's fledging experience: I THINK Little probably went all the way to the ground on July 4. There are not that many limbs below what you see near the nest in the camera view and our savvy landowners can easily scan them There is no way Little could have climbed back up (although some raptors can in lesser trees) since the bottom 50 feet of this nest tree has no limbs to aid the ascent. Even with a forward flip start, it is likely that some wing flailing lessened the speed of his descent and effectively cushioned his fall.

4) Grounded fledglings: Most take short flights to higher limbs in adjacent trees to regain heights and return to the nest. This could take a day or more, especially during the foggy conditions recently prevalent near the eagle cam'. Some fledglings have more skill (or luck) with first flights, but smooth landing are a mystery that escapes most fledglings for a few days. The hops and lunges from the nest to surrounding limbs are good practice, and all flapping motions help build important flight muscles. Remember, Big & Little have been stationary in the nest for most of their lives so more exercise, gradually longer flights, and time are all important ingredients to their development on-the-wing.

5) Bruised leg? Little may have had a bruise of other soft tissue injury from his fall on July 4. It was not a broken leg. Such an injury would have prevented a return to the nest, clinching food, etc. One-footed perching is not that unusual, especially on slanting limbs as many are around the nest. Most viewers seem to notice steady improvements, concerns have lessened, and admiration for the fledglings' development is dominant in the blog. Enjoy!

6) Interventions: Unless a serious injury manifests, the fledglings are much better off with adult parents than being taken into captivity for veterinary attention or rehabilitation. The coming weeks are their ONE chance to learn survival skills while still living a guarded existence with Mom & Dad. Note the incredible restraint that the landowners demonstrated during the shaky fledging period: well done! We were all curious about the fate of the eagle cam' fledglings, but this development period is critical both in the short term and chances for future survival. Interventions for Little could have jeopardized Big in this crucial period and could not be justified unless absolutely necessary.

7) The next week: As long as the family group is together and disturbances are minimized, I doubt that inadequate food will be a factor at this stage. Little seems to occasionally get the edge in food squabbles. Which eaglet prevails at any given feeding might only reflect which one is hungrier. When both are content, indeed there is harmony at the nest. They will lay prone in the nest less and less as time progresses, and eventually time spent at the nest diminishes. I know you miss seeing the adults, but their absence from the nest encourages the fledglings' development. As noted before, one or both are usually watching carefully from a nearby. For example, I once watched an eaglet alone in a nest for 4 hours with no adult in sight, when an osprey circled twice overhead. The eaglet gave an alarm cry, and both adults were chasing away the intruder within 15 seconds ... but I had not seem them at all until that moment of need! The fledglings are usually inept at catching food so adult eagles will continue to make food drops at the nest or at other locations frequented by the fledglings.

-- Charlie Todd, Maine Dept. of Inland Fisheries and Wildlife

Friday, July 07, 2006

July 7 notes: TWO eaglets - no rescues needed!

Dear friends of the eagle cam' and well wishers for our fledgling eaglets:

Take a deep breath, relax, and enjoy continued viewing on the eagle cam'. Both fledgling eaglets are DEFINITELY still present and closely guarded by both parents. After the aerial survey flight was cancelled today, the boss (Barb = my wife!) convinced me that we should carefully patrol the nest vicinity to make sure all is well. By reading your blogs, it's clear that many were tormented by the unknown fate of both eaglets after fledging on July 4. (There's anxiety in our household as well!)

Please, never visit an eagle nest where fledglings are freshly on-the-wing unless you are advised by a biologist and know how to handle an eagle in the event of a mishap! We spend most of our time moving cautiously and scanning the vicinity while one eaglet is above in the nest. We do not want to excite it into flight since many fledglings prefer to prolong their homecoming and delay their next flight as long as possible after first returning to the nest. We do not want to scare our missing eaglet -- whether perched in a tree, standing by the shore, or injured and hiding in understory vegetation. Most of all, we do not want to trigger adults into circling flights and vocalizations protesting our presence because this will certainly alarm the entire eagle family.

We inspect the area beneath the nest: relieved not to see a dead or injured eaglet. The resident landowner shows us an area of matted grass where something large bedded on the ground for a while, but we all remain uncertain. I patrol the shoreline bluff, and Barb walks along the water's edge. At 11 am EDT, one adult flies quietly from a lofty pine 100 yards west. Fortunately, there are no aggressive displays or cries of displeasure. After we pass this perch, Barb briefly glimpses a dark eagle follow the same flight path: a smooth glide with only a few wingbeats out of sight and around the bend of the shore at least 250 yards away. Was that really the missing eaglet? Is a 2-second observation out of the corner of your eye adequate reassurance? She's not satisfied ... I assume that eagle cam' viewers won't be content either!

We wait and watch. The perched adult frequently looks down over its shoulder: the watchful eye of a parent. There's no way to see a nearby eaglet from our vantage point, but that's not surprising. Fledglings have more trouble landing than flying! It may be on a lower limb than the adult's high, conspicuous perch. We stay back and are eventually rewarded with several "eaglet squeals" originating from the trees well east of the nest. These yelps for attention (or food) are typical of young eagles. We retreat and compare notes with the landowners. The eagle cam' is hard wired to their TV, and they report with confidence that the eaglet in the nest has been stationary and silent throughout our search. These are all the clues we can hope to gain today: the third day after fledging when the family group is adjusting to life out of the nest. It is best to stay back and let eaglets develop life skills from experienced adults. There is no way our interventions can improve the situation.

Part of this process may evolve outside the view of the eagle cam' but I would be shocked if you do not see "Big" and "Little" at the nest during the next 2 months! Their use of the nest will diminish gradually. If they really don't get along that well, they may not spend much time there together. (If we can do this next year, we will band the birds to aid identification, but looking at behavioral tendencies is a good strategy to distinguish them. However, if one eaglet was displacing the other from a preferred perch, habits may change when they have solitary time in the nest.) Adults will purposefully minimize time in the nest so as to encourage development of the eaglets. Sometime in September or October, family ties end. The eaglets disperse. One Maine eaglet appeared as far away as South Carolina by November of its first year!

The landowners (gracious hosts of the eagle cam') welcomed our visit, shared insights, and provided delicious lobster salad sandwiches after our mission was complete. They have experienced 14 consecutive years of successful nesting so they have perfected the art of co-exisitance with nesting eagles. Apropriate stewardship is key to safeguarding the remarkable recovery of bald eagles. After >28 years on the Endangered / Threatened Species list in northern states (>37 years in the southern U.S.), future delisting of bald eagles will lessen some regulatory protection and may result in less frequent survey monitoring. Owners and neighbors of nesting eagles can play important roles. We are eager to assist. Let's hope the other 402 pairs of bald eagles nesting in Maine this year have as much luck in coexisting with humans as these birds!

Management comments: National guidelines have been drafted to promote a lasting recovery of bald eagles. In Maine, our annual population monitoring and regulatory protection of nests will continue until the Threatened Species status is removed by the legislature. Our agency will only recommend state delisting after sucessfully implementing a habitat safety net which includes a mix of land conservation and stewardship roles of private landowners. Agencies will adjust management strategies after bald eagles are delisted. Your support is always welcome. -- Charlie Todd, Maine Dept. of Inland Fisheries and Wildlife

Wednesday, July 05, 2006

July 4 Fledging!!!

So apropos...our both eaglets fledged on the 4th of July! Jane, one of our viewers provided recordings of both fledging events, which can be viewed at the web links below. I am including Jane's report and Charlie Todd's response. No one was in the nest this morning (July 5), but we expect both birds to occasionally visit the nest from time to time over the next few weeks. After they gain better flight skills, they return to the nest as a convenient place to feed and perhaps even roost for the night.

After fledging the chicks stay in close proximity of the nest for a month or two before leaving their parents and dispersing from the nesting area. As part of my doctoral research, I observed 18 young eagles during this phase of their life. After fledging, the young birds develop their flight skills, but apparently have no interest in learning how to hunt. After thousands of hours of observation, I never saw a fledged eaglet attempt to forage on its own. They fly from tree to tree begging food from their parents. Eventually, the parents get tired of this game and the young birds drift away from the nesting territory. They must eventually learn how to find food on their own.

Where do they go after leaving home? From our banding studies, we know that about 30 to 60 percent travel long distance south along the Atlantic seaboard during their first winter. Young eagles from Maine have often been observed in the Chesapeake Bay region, western Massachusetts, New York, Pennsylvania, and New Jersey. The balance of the fledged eaglets wander around Maine for their first winter looking for easily-obtained food. About 75% of the eagles survive their first year. By their second or third summer, most return to Maine to stay and eventually nest at age 5 or more. Few of our banded eagles are known to be nesting outside of the state.

Check in on the nest from time to time. You may be rewarded with an observation of "Big" or "Little."

Mark McCollough, U. S. Fish and Wildlife Service

Jane: Yes, I saw this comment in the blog -- amazing reception that these birds have had. Publicizing fledging was bound to create lots of concerns. Landowner assures me there is no eaglet on the ground, and I've asked him & neighbors not to search the woods for a potential rescue: better to let the adult eagles take care of that task / keep the family bond intact. It's quite foggy on the coast July 4 - July 5 am so not likely there'll be much movement there until clearing. I may get to fly that area today so will try to get visuals on the birds. -- Charlie
-----Original Message-----
From: Jane Edwards
Sent: Tuesday, July 04, 2006 1:18 PM
To: Charlie Todd

Subject: videos of Eaglets leaving eagle cam nest

There's a web page that keeps up with the Maine eagle cam and they evidently have been watching the video constantly, because they can go back and compile tapes from it. That issue aside, I thought I'd forward to you the departure of "Big" and "Little" from the nest. Hope you can "play" them on your computer.
I looked at "Little"'s departure very closely on some other video that showed clearly what happened. He flew up, trying to get back in the nest, but he landed on a branch that was way too small for his talons to grasp and get a grip on. When he tightened his talons on it, he spun right around in an upside down position, and then he let go and fell head down. Hope he's okay.
Begin forwarded message: