Friday, June 30, 2006

June 30 notes: the trials & tribulations of fledgling eaglets

" ... one bumbling tumble for bald eagles ..." Yes, astute observers of the eagle cam witnessed a less than stellar exit from the nest by our smaller eaglet about 4 pm EDT today, June 30. I have to be honest: I didn't see it, but a barrage of phone calls soon confirmed that this complicated process of flight is underway at the eagle cam!

Many are concerned for its fate because this maiden voyage looked more like a flop / fall than a flight. Fear not: I called a neighbor who sees the bird on a limb beneath the nest, while "big sister" remains in the nest. As Mark described in our last Journal entry, nothing surprises us about first flights, first landings, and the entire early fledging period. It is indeed a high risk time, and therefore, perhaps more compelling to watch. We have zoomed out the camera to give a wider angle view of the entire nest and surrounding lateral limbs of the nest tree so perhaps more of the process will be in view for those who dare to watch!

Actually, all is going well at the eagle cam. Here are some brief notes from other nests around Maine to give you a taste of the many challenges faced by nesting eagles:

A Sagadahoc County nest has triplets when Chris DeSorbo and I visited the nest on May 15. Chris and Bill Hanson combine to band eaglets and obtain blood samples for monitoring dietary mercury. One of the three 4-week old eaglets is smaller than its siblings. Since Maine is planning to donate an eaglet from 3 different nests to a reintroduction in Vermont, we immediately broach the idea of removing one here with the very conscientious landowners who are agreeable. We have to wait to find a "set" of appropriately aged eaglets. Chris visits 3 weeks later and finds only two eaglets: a repeat incident of what happened a few weeks earlier at this eagle cam. The same outcome reduces broods of 3 eaglets at a nest in Kennebec County and one in Waldo County. When food is limiting or harsh elements challenge an adult's ability to care for all nestlings, only the strongest survive. We look elsewhere for eaglet donations to Vermont.

A Penobscot County nest with poor productivity has been closely monitored since March as part of special research monitoring dioxins in Maine eagles. It's a priority sampling site for the mercury study as well. Two addled eggs were recovered here in 2005. We are all pleased by their apparent success this year when my May 23 flight revealed two 4-week old eaglets standing in the nest. On a June 1 flight, only scattered remains of both dead eaglets are visible: the victims of scavenging ... or possibly predation. Chris finds two 6-week old eaglets dead in a Washington County nest later in June that were likely killed by another predator. Our climbing crews have now recovered 5 dead eaglets in little over a week. Tissues will be tested.

On June 5, wildlife rehabilitator Anne Rivers follows up on a report that 2 eaglets are on the ground at a Hancock County nest. She retrieves them; feeds and rehydrates them for 3 dyas; and gets a veterinary exam, blood tests, and full body X-ray. I investigate the site and find the nest 100% fallen and a neighbor who has lost 10 hens to predators. The birds would not have fared well here, and they become (by default) our first "volunteers" to move to Vermont. They go home with me and get a 50-mile head start on their 400-mile trip. Haddock for dinner!

Good news from other locations: there are healthy sets of triplets at 3 Kennebec County nests. Eagles did not nest in Kennebec County between 1975 and 1994 as past declines decimated eagle numbers near Maine's state capital. One of the triplets is at the last Kennebec nest occupied in 1974 before their disappearance and where eagles returned to nest in 2001 after a 27-year absence. The landowner recalls when "his eagles" were the beneficiary of an egg transplant in 1974. The karma is good, and on June 8 we take the smallest eaglet away to join Maine's donation to Vermont. Bill Hanson climbs the tree on a very rainy day and soon after I am driving away with my wife holding a wet eaglet on the passenger seat so the bird will show up dry in Vermont. Only 10 miles down the road of its 250-mile journey our passenger shifts its weight, does a headstand, and does what all well-fed eaglets do. ("Eagle cam" watchers all know what happens next!) I am plastered by eagle poop at point-blank range. My sympathetic wife eventually stops laughing and orients the eaglet in another direction just in case. The transfer of 3 dry eaglets for Vermont is completed a few hours later. I look for a change of clothes!

Here's one final anecdote to show that sometimes we can remedy pending eaglet losses. Chris climbed another Sagadahoc County nest on June 12 and bands a 4-1/2 week old eaglet with large facial inflammations below its eyes. Bill Hanson returned to the nest on June 27 with wildlife rehabilitator / clinician Marc Payne who lanced the swollen sinuses and administered an antibiotic and sutures. It's pretty clear that this bird would not have made it without some help.

Management comments: Research at eagle nests and interventions with nestlings is always conducted in small windows of opportunity to minimize risks. Eaglets aged 4 - 7 weeks old can withstand the interruption and brief lack of parental care. Thus, we were not tempted to intervene at the "eagle cam" nest when the third eaglet was lost in just its third week: risks to its siblings could not be justified. Wildlife managers often prescribe timing safeguards to minimize potential disturbances near nesting eagles. The timing and unique circumstances of each location are considered in combination. As you watch fledgling eaglets in the difficult early stages of life out of the nest, please realize that this is another sensitive period when eagle nests can use all the privacy we can afford them. -- Charlie Todd, Maine Dept. of Inland Fisheries & Wildlife

Monday, June 26, 2006

June 26 notes "Fledging any day now..."

Our young eaglets are growing fast and now look like real eagles. "Big" (as many of you like to call the largest bird), was hatched on April 10 making him or her 11 weeks old, and "Little" is about 4 days younger. Both eaglets are approaching the size and weight of their parents. In fact, young bald eagles have longer wing and tail feathers than their parents (biologists don't know why).

As astute viewers have observed, the adult eagles are rarely seen now except to make a quick prey delivery to the nest. They don't bother to tear the food apart, but allow the eaglets to carve up their food with their sharp beaks. Usually, the adults are within site of the nest (or perched out of view of the camera high in the nest tree). Adults on the coast of Maine have feeding territories up to a mile or two away from the nest depending on the location of feeding areas and competition from nearby nesting pairs.

About two weeks ago our eaglets started "limbing out," that is leaving the nest and perching on adjacent limbs. They don't go far from the nest and remain in camera view. Don't be surprised to see them start to fly/hop from limb to limb or nest to limb. Watch for the eaglets to grasp hold of a limb or the nest and beat their wings vigorously. This behavior accomplishes two things - first, its strenghtens their wing muscles in preparation for their first flight, and second, its gives the birds a good sense of the size and power of their wings. It takes considerable agility for bald eagles to fly in and out of trees with a 7 foot wingspan, and these pre-flight routines help them guage their own size. On breezy days, watch for the eagles to extend their wings and float briefly into the wind before settling down on the branch again. Sometimes they will snatch a branch from the nest and float into the air with the limb in their talons. A large portion of the day is spent preening (adjusting and oiling) their new feathers.

"Big" could make his or her maiden flight any day now. I studied the "fledging" phase of bald eagle ecology years ago as part of my doctoral research at the University of Maine. Young bald eagles make their first flight at 11 to 13 weeks of age. What makes a young eagle decide to leave the nest? After watching about 20 eagles fledge, I can't say for certain. I never saw the adults encourage the young to fly or to entice them away with a food item. Just like kids, I believe they just know when its time to try out their new wings!

On many occasions I witnessed the first, awkward flights of a young eagle. I recall that many times this occurred during one of their floating-into-the-breeze experiments when they missed the branch or got blown by a gust of wind. Suddenly, they realize they are airborn with nothing but a great void underneath them! The young eagles don't know the art of soaring and thermals, so they begin flapping vigorously. Since eagle nests (like this one) are located near water, the first flight is along the shoreline over a lake, ocean, or river. Usually, the first flight is no more than 200 to 500 yards. The shoreline environment provides many opportunities for landing - a log or rock on the shore, low trees, or maybe a large white pine. I've seen young eagles land in the water and row to shore with their wings. More often, they try to land in a tree. On several occasions I watched young eagles land on branches only to have their momentum carry them forward so they end up hanging upside down with wings extended like a giant bat. On other occasions I've seen them tumble from branch to branch in a tree until they desperately grasp a perch or talon full of twigs to stop their fall.

Adult eagles don't seem overly concerned that their young have fledged. "Big" will squawk and squeel at its parents when it gets hungry or if it sees the adult returning to the nest to feed "Little." A week or two after fledging, the adults will start to deliver food to the fledged eaglets in nearby trees. Although it is difficult for eaglets to learn how to grasp a fish with one foot and hang on to the tree with another. I've seen many a disappointed fledger hang their head in discouragement after fumbling and dropping a fish just delivered by its parents.

Fledging is a dangerous time for young eagles. They can get injured during their first flights. Sometimes, boaters will encounter an injured eaglet and bring it to us for rehabilitation. They are also vulnerable to predators. Young eagles who land on the ground will "climb" a tree by evening by hopping upward branch by branch. This gets them out of the way of ground predators like raccoons and foxes.

Don't be surprised to visit the webcam in the next week and only see a single eagle in the nest. "Big" could go any day. Once eaglets leave the nest, they usually develop the flying skills (or hunger) to make the flight back to the nest within a few days. The nest will remain a center of activity for the eagle family through the summer and serve as an easy landing spot for future feeding.

Mark McCollough, U. S. Fish and Wildlife Service

Thursday, June 08, 2006

June 7 Notes - banding eagles

From our eagle surveys, we now know the web cam eaglets are among the oldest in the state. Their baby down is rapidly being replaced by dark brown contour, wing, and tail feathers. The feathers grow from blood quills, which you can see at the base of the large wing feathers in the last picture posted above (they look like a blue drinking straw). Young eagles are chocolate brown in color. They do not get a pure white head and tail until about five years of age. Their beaks and iris are dark brown and will not start to turn yellow for another 2 or 3 years. Both eaglets are growing rapidly and likely weight about 6 to 8 pounds - about 1/2 to 2/3 the weight of their parents. At this time the chicks are starting to exercise their wings, but they have to be careful or they will damage the blood quills. The wing beating exercises will increase in frequency in another week or two when their wing and tail feathers are fully developed and harden. As observers have noted, the adults are rarely within view of the web cam, but they are nearby hunting and guarding the nest. You've also noticed that we have been getting a lot of rain in Maine in the last two weeks. These chicks are likely old enough to tough it out without Mom's help, but I've seen them often huddled together to keep warm. Younger chicks don't fare as well. We've already documented several advance-aged chicks that died in other nests during our aerial surveys.

Since the early days of eagle recovery, biologists in Maine and elsewhere have used banding as a technique to learn about the movements and survival of bald eagles. When we band eagles we secure a small, individually-numbered metal ring or band on the legs of eagles to individually identify each bird. The birds wear the band for life. Eagles seem to get used to the bands like a ring on a finger. In the 1980s, we attempted to band all bald eagles in Maine and New Brunswick. For over a decade tree climber extraordinaire Barnie Thompson of Brewer, Maine climbed every eagle nest with young. Barnie climbed his last eagle nest several years ago when he approached his 70th birthday.

This June, tree climbers Bill Hanson and Chris DeSorbo (pictures above) are climbing nests in interior Maine as part of a study to evaluate the effects of mercury and organochlorine contaminants on eagles. (The eaglets at the web camera nest will not be banded.) Climbers use boot hooks, ropes, and safety equipment to climb trees. Although bald eagles are a large bird of prey, they do not defend their nest or attack the climbers. The adults often circle overhead and vocalize while the climber is in the nest. The climber gently places the 4 to 6 week-old eaglets in a canvass bag and slowly lowers them to biologists on the ground. Each chick is weighed and measured. Blood and feather samples are taken for the contaminants analysis. The metal bands are secured loosely around the leg and riveted in place. A red band with a large letter-number combination is a unique identifier for Maine eagles (other states and provinces each have their own assigned color bands) and aids with idenfication of birds from a distance. A standard U. S. Fish and Wildlife Service band has a unique number stamped into the band. The chicks are then hoisted back into the nest in the canvass bag. We gather prey remains at the base of the nest to learn more about eagle diets. The entire process takes about an hour.

Important information is learned from banding. Band numbers are retrieved from dead or injured eagles, and sometimes band numbers are read and reported by eagle watchers. Banding provides information on eagle movements. We've had eagles from Maine recovered or observed in as far away as Labrador and North Carolina. We've seen eagles in Maine banded from as far away as Saskatchewan, Nova Scotia, and Michigan. Repeated observations of banded eagles over the years are used to estimate survival rates of eagles. As part of my doctoral research, I read the band numbers from hundreds of eagles visiting winter feeding stations with a spotting scope and used the information to document survival rates for young and adult birds. Banding also provides information on how old eagles live in the wild. Recently we recovered an adult eagle 23 years after banding it as a chick in the early 1980s.

We do not band all the eagle chicks in Maine each year. Although biologists in some states routinely band all of their eagle chicks, we only band the birds for directed studies. We are no longer reobserving eagles at winter feeding stations to document survival rates. This summer, eaglets at selected nests are being banded in conjunction with a contaminants study.

Mark McCollough, U. S. Fish and Wildlife Service