2012 Nesting Season Information
This camera project would not have been possible without the major support of: OG&E, OneNet, Atlas Broadband, OU College of Arts and Sciences, University of Oklahoma, Oklahoma Biological Survey, U.S. Fish and Wildlife Service, ConocoPhillips. Additional support provided by individual donors.
31 July 2012: The young have long ago fledged from the nests this summer. We typically leave the cameras running this time of year even though there is not much to watch, but we really don't spend time repairing them if they stop working this time of year (the off season). We will be repairing and replacing equipment later this summer or fall in preparation for the next Bald Eagle nesting season which will begin in November or December. We don't have an ETA for this work, but in the meantime, ten Bald Eagles that hatched in Oklahoma can be tracked on the tracking section of our website.
19 April 2012: The young eaglelets at the Sequoyah nest have been "branching" for some time now. This is the process of beginning to leave the nest as they perch on branches near the nest. While they may not be reliably visible on the nest cam at this point, they will likely return to the nest occasionally for some weeks yet, using it as a "home base" while they learn to fly and hunt. The younger eaglet at the Sooner Lake nest is changing in appearance as its gray down is being replaced by darker feathers growing in.
29 March 2012 (Sequoyah): Feeding by the adults is less frequent now, but greater amounts of meat, such as from a captured duck, may be consumed at one feeding. As the youngsters approach first flight, feeding by the adults can sometimes be as infrequent as every 2-3 days as the birds naturally "lighten up" in preparation for their launch into the air. If adults are feeding small food items, such as softshelled turtles or shad, however, they may feed more frequently.
We had planned to attach GPS transmitters to the Sequoyah eaglets last week, but the ill-timed heavy rain event prevented access by the large bucket lift needed to reach the nest. The age of the chicks is crucial for applying the transmitters. The chicks must be old enough to have reached full body size, but not so old that they are likely to prematurely jump out of the nest upon our approach. We feel that they are now too old to risk capturing them, so we will not be able to outfit these eaglets with tracking devices. We still hope to outfit six eaglets with tracking devices this season, and we are actively monitoring a number of nests in northeastern Oklahoma for chicks of the right age in nests that can be reached.
26 March 2012 (Sequoyah): We have encountered another kind of technical difficulty to add to our growing list of problems that have caused video outages over the years. We have experienced all types of problems, from intense precipitation to camera cables chewed by packrats, muskrats, or beavers. Lightning strikes have blown out cameras or have hit and killed incubating eagles directly (at Sequoyah, prior to our nest camera project). The Sequoyah cameras were off and on for several days recently, and a site visit showed that a colony of ants had invaded our electronic equipment box. While viewers from Texas or the southeastern U.S. may have heard of the problems sometimes caused by exotic Raspberry crazy ants (we aren’t making up that name!) getting into electrical equipment, it is likely that in our case native ants living near the nest site were seeking refuge from the recently flooded ground below the nest, and found our dark, dry equipment box a convenient escape. We will soon be replacing damaged equipment resulting from this latest challenge.
22 March 2012 (Sooner Lake): This video clip from the 14th shows the second egg pipped prior to the chick hatching.
This video from the 14th shows the second chick after hatching.
21 March 2012: The Sequoyah cameras have likely stopped working due to the extended overcast weather we have had. They will likely come back when things get a bit brighter outside. A recent interview about our nest camera project was aired on KOTV, Tulsa's CBS television affiliate. It can be viewed by clicking this link.
20 March 2012 (Sooner Lake): As most viewers know, one of the young chicks disappeared over the past weekend from the Sooner Lake nest. I have reviewed the clip showing the adult stepping on the chick (http://www.youtube.com/watch?v=xc926dOI1fA). Actually, such incidents are not uncommon in raptor nests, and while the adults usually "ball their feet up" around unhatched eggs and around "just hatched" young, as the chicks begin to grow, parents sometimes step on their chicks accidentally with open feet or when focused on threats near the nest. Usually, the sharp talons do not have any impact on the chicks, as the primary contact is between the pads on the bottom of the adults' feet (rather than the talons) and the chick.
I have seen tame, captive adult breeding falcons step on their chicks numerous times, perhaps over one hundred, but have never seen a puncture as a result from such accidental "pressure" treading by a calm falcon. Captive breeding falcons that are wild, on the other hand, can accidentally step on their chicks and do serious damage when trying to protect them from a human intruder. For the falcons, extent of damage can be affected by the substrate beneath the chick that is pressed by the adult's foot. Falcons do not build stick nests as do eagles, but instead scrape out a depression in the dirt where they can lay, incubate, and hatch their eggs. In captivity, their scrape or depression is excavated from about six inches deep of quarter-inch pea gravel. This gravel gives away slightly beneath the chick that finds itself occasionally beneath an adult foot.
The nest lining in an eagle nest serves the same purpose. It pads the incubated eggs from the sticks comprising the nest, and it also pads the chicks that lie beneath the brooding adult. Therefore, the lining helps pad the chick that might be "stepped on" by an adult eagle. The eagles we are observing were not upset and were not protecting their young; instead, they were going about daily life in a calm manner. In my opinion, the eagle chick that was momentarily beneath the eagle's foot suffered no damage. And, it is normal for the adults to reach down and "scoop" the chicks back underneath them by using the adult's beak. The fact is that we really have no idea about the cause of what happened to the deceased chick, and we will probably never know. It is important to refrain from deriving conclusions when we have little or no evidence regarding cause and effect. That is why we need sample sizes with many observations before we can draw conclusions. It is documented that adult birds become better parents with age and experience as evidenced by their increased number of annually fledged young. We are sorry we cannot offer any more definitive answers in this case. We know only that young eagles sometimes die in the nest for a variety of reasons.
Dr. Steve K. Sherrod, Executive Director
14 March 2012 (Sooner Lake): The second chick at Sooner Lake has hatched!
With chicks newly hatched/hatching at Sooner Lake and with 7-8 week old chicks at Sequoyah, this is a good chance to compare the difference in feeding schedules by adults as chicks develop. Viewers will note that the newly hatched chicks are fed tiny bites many times daily, usually approximately every 2-5 hours. Feeding amounts and times can depend on the type of food fed previously (fish usually provides less caloric energy intake than do red-meated ducks and coots), the amount fed during the previous feeding (chick w/full crop or only partial crop-can be result of food begging competition to parent; how hungry the chick is; how aggressive older chicks are to younger chicks, thus resulting in cowering behavior by subordinate chick and little or less food consumption during feeding bouts), weather (chicks consume more food during cold weather), the amount of time the chicks are brooded by the parent and thus how much energy is expended for the chick to keep warm, and adult hunting skills and frequency of prey delivery.
The older chicks are now at an age where they can consume large amounts of food at one time. Their crops serve as containers where protein and other food, once consumed, can be stored and gradually digested throughout the day. Up until this stage, their bodies have been growing constantly, almost to full size, but now, their growing, blood filled, flight feathers including primaries and secondaries on wings (remiges) as well as tail feathers (rectrices) are where most of the energy is going. While the little chicks at Sooner Lake keep food (energy) moving constantly through their bodies by frequent feedings from adults of small amounts into tiny crops, the larger youngsters at Sequoyah are only fed as little as twice a day, once a day, or even every other day. For the dedicated nest watchers, it is interesting to count and compare the number of feedings of chicks in each nest, starting at dawn's first light and ending at dusk. This should be done for several days in order to average out feedings due to variables described in the first paragraph. If counting all day is too much for one person, perhaps you can "tag team" it with the coordinated help from other viewers on the chat room.
12 March 2012 (Sooner Lake): The first egg hatched yesterday! The first video below shows the adult moving half of the eggshell up out of the nest bowl last night. The second video below shows the chick being fed today. The bottom photo below shows the chick this morning.
9 March 2012 (Sooner Lake): Viewers watching this afternoon may have seen the moment when the new Sooner Lake nest camera (on the lower right, above) came on. This is something we have been working on for some time, and we had a number of technical difficulties to overcome, along with our eagle cam partners identified above and below. We are fortunate to have this view, as we will relate below.
The Sooner Lake eagles once again chose to nest at a site other than the pole shown as the lower left image above. The site they chose to use this year is the same one they used two years ago, in which chicks fell out of the very small and poorly constructed nest. Since then the adults have made substantial additions to this nest, so while still not large by eagle nest standards it is in much better condition than it was two years ago. Because we had left the cameras in place after the disastrous 2010 season, and they very fortunately still worked upon testing them, we were able bring this video feed back online with a lot of effort but with minimal disturbance at the nest site.
The lower two camera views might now be a bit confusing to viewers because the wide cam view on the left is of the tower, while the close-up view of the nest is an alternate nest site for this pair in a dead tree some distance away. We decided to retain the wide view of the tower because the adults still occasionally perch within viewing range of this camera, and conditions at the currently used nest prevent a good wide cam view.
This Sooner Lake nest is typically one of the latest in the state to get eggs, and this year is no exception. We do not know the exact date of the start of incubation for this nest in 2012, but the first of the three eggs could hatch any time between now and about two weeks from now.
Three eggs in the 2012 Sooner Lake nest. We do not know exactly when incubation began, but they should start hatching the second or third week of March. The pair is using the same nest that was used in 2010, although they have added material to greatly improve the condition of the nest.
8 March 2012 (Sequoyah): Viewers are now witnessing the reality of competition that occurs among siblings in an eagle nest, and, really, in many families of living organisms. For eagles and some other raptors, this begins with the temporal pattern for incubation of the eggs and the resulting order of hatching, and continues throughout nest life, as well as even beyond through post-fledging dependency. In this case, and as we have already presented, the first hatched young gets off to a head start in growth by consuming fully gorged crops of food without any competition during feeding bouts by the adult female. This chick is soon followed by the next hatched, and both of these siblings receive ample food as long as prey is plentiful and hunting by the adult male is good. The last hatched chick gets off to a disadvantaged start, being several days behind, smaller with less strength, and subject to the domination of its siblings during feeding and competition for brooding by the adult female. Thus, not only is chick 3 smaller, but it is later in development including feather growth. The third chick hatched 29 January, so it was approximately 5 ½ weeks old. However, although still growing, it was somewhat stunted, and thus was really about 4 weeks old for comparative purposes, all the time losing the competitive race for survival.
When a chick is starving, its head tends to grow large, accentuated by a body that becomes quite stunted. In the Sequoyah nest 2012, the third chick though small was still growing nicely, with well proportioned body and head. This winter's weather has been mild as we all know, and with little precipitation except for a light snow right after hatching when the adults were brooding the little chicks. Down provides warmth to the chicks especially during calm, dry weather, but unless it is covered with the dark brown body feathers seen on the older chicks (similar to a waterproof shell over a down jacket), this insulation provides little thermal protection when it becomes soaked. In this case, no longer brooded by the adults and unable to shed the cold and blowing rain, this chick has likely died of hypothermia. We all know how much colder we quickly become when subjected to both rain and high winds when without a shell (or adult feathers in the case of this eaglet).
In this case, we will likely soon see the adults feed the dead chick to its siblings. This is conservation of energy and commonly happens when one of the young expires. In some cases the adults will carry the dead young off or it can even become buried among the debris in the nest, but likely it will be used as food. We will wait to see what happens, but whatever occurs, this is the reality of eagle reproduction. It is disappointing but not surprising for a third chick to succumb to any one of several possible challenges. Had the weather stayed warm and dry for another week the outcome may have been different.
To follow up on our March 5 post, we cleaned the camera covers at this nest, with the help of a crane provided by the Sequoyah National Wildlife Refuge. This consisted of simply soaking the globes with water from a mister bottle and wiping them with paper towels. We also moved the lower camera about 20 inches higher to try and keep it out of the line of fire by the youngsters. The higher camera has been in the exact same place this season and past, but the adults perching high above in this tree managed to hit it this year with a slice. When we installed it, we realized that the lower camera would be a good target for the developing young, but the adults ended up building the nest about a foot higher after our installation which increased this camera's vulnerability. Oddly enough, there were no whitewash splashes from the nestlings that reached even so much as an inch higher than the lower camera as it was originally mounted.
5 March 2012 (Sequoyah): Well, that looks better, doesn't it? Today we were able to clean the camera lenses (which is much easier said than done). Those who watch regularly have probably seen the eagles' ability to discharge waste some distance, and unfortunately some of it had marred the view through the camera lens for well over a week. We also moved the camera up a little higher, which with luck will help prevent the lens from becoming obscured again.
This photo shows the foot of one of the older chicks, as well as the developing
flight feathers beginning to break out of their sheaths. The yellow feather in
the nest appears to be from a Northern Flicker.
The three eaglets in the Sequoyah nest hunkering down. The youngest chick
is still in its coat of gray down while the older two are growing first feathers.
2 March 2012 (Sequoyah): There has been some question on the eagle cam comment section about whether or not siblicide (the killing of one sibling by other siblings) exists in bald eagles or in any other birds for that matter. Unfortunately, Sutton Center biologists cannot address all the questions that arise on the site since our staff continues to keep very busy, but we will briefly try to share information on this subject since infanticide/cannibalism/siblicide has intrigued scientists for decades and is a focal point for some aspects of sociobiology. Following the material we present below, we also provide a number of references that the reader can examine in order to become better informed on this very real phenomenon.
Bald Eagles as well as some hawk and other eagle species sometimes kill their siblings and/or their young, depending on special circumstances. Direct observations of this phenomenon are rare, but with the advent of nest cameras will likely be documented visually to a greater extent. When I was studying some 70 plus Bald Eagle nests as well as eagle wintering behavior (data for 1969-1974) in the Aleutian Islands, I found that nests with two young had higher chick mortality than nests with one young which would suggest food stress. We had no nest cameras, but often smaller chicks were found to be healthy on one visit but half eaten on the next. This means the dead chick could die of starvation or exposure, die of sickness, be killed by his/her sibling, or be killed by the parent. Probably all of the above occurs as portrayed below.
I have observed captive breeding gyrfalcons with young kill a sick offspring and feed it to the offspring's sibling even when excess food was available. While appearing maladaptive to feed a sick youngster to another sibling, apparently economy of food supply is more important than the risk of disease. Usually infanticide would occur only in such special circumstances (offspring show abnormalities or disease) unless the offspring are not related to the killer that consumes them. Second or third hatched young have a disadvantage in weight gain and size, and thus are more frequently killed by their older siblings or simply die due to an inability to compete adequately for food from the feeding parent with their larger sibs. If they do die, the parent feeds them to their siblings to conserve energy by the hunting parent.
At the Sutton Center, we hatched and raised nearly 300 bald eagles over an eight year period. As soon as the down of hatching chicks had dried, most chicks almost immediately began attacking other "just hatched" chicks vigorously by "hammering" with their beaks, grabbing on, and shaking. They had to be separated physically to prevent siblicide during that period. We concluded that in the wild, the only thing that kept them from killing each other as hatchlings was the physical presence over them of their brooding mother, or in our case, a folded towel. As long as they were in the process of taking food offered them, the chicks did not attack, but would often do so in between bites. This aggressive behavior among siblings disappeared by the time the chicks were six weeks old (of a 12 week nest life before first flight). Apparently by six weeks of age, perhaps by how much weight they have gained thus far, the siblings can ascertain if there is going to be enough food that season to raise them and their sibs, and their efforts to eliminate their sibs, dissipates.
Older egret nestlings sometimes also kill their siblings or oust them from the nest, and first/second laid egret eggs have been found to have higher steroid levels than later laid egret eggs. Eagles have been studied extensively and are thought to actually regulate the sex of eggs (females being larger and demanding more food) produced depending on the amount of food available to the adults within their hunting ranges during a given season. Please read the following peer-reviewed scientific publications if you are interested in siblicide, infanticide, or cannibalism in theses fascinating birds. Abstracts or excerpts are shown below, but most require subscriptions for access to the full paper, or can be obtained through a research university library.
Steve K. Sherrod, Ph.D., Executive Director of the Sutton Center
Citations for further reading, below:
Buehler, David A. 2000. Bald Eagle (Haliaeetus leucocephalus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/506/articles/introduction
In Saskatchewan, second chick hatched in a clutch showed delayed development compared to first (n = 38; Bortolotti 1984b), and chicks with hatching interval of 2 d showed greater differential growth than chicks with hatching interval of 1 d (Bortolotti 1989), presumably because of differential nutrition. Hatching asynchrony and differential growth leads to differential mass in siblings, facilitating competition and fratricide (Bortolotti 1986a). Sibling competition and mortality is greatest early in nestling period, when size differences are greatest (Bortolotti 1986a). Third-hatched chicks in Saskatchewan nests received little food and usually starved. In 1 nest, mass of 9-d-old, 8-d-old, and 6-d-old siblings were 477, 260, and 80 g, respectively (Gerrard and Bortolotti 1988).
Does sex-biased hatching order in bald eagles vary with food resources?
Dzus, EH | Bortolotti, GR | Gerrard, JM
Ecoscience. Sainte-Foy [ECOSCIENCE]. Vol. 3, no. 3, pp. 252-258. 1996.
In birds that exhibit sexual size dimorphism, hatching asynchrony, and siblicide, the probability of nestling mortality and the cost of rearing young may vary with different combinations of sex and hatching sequence. When food abundance varies spatially and temporally, parents may maximize their fitness by manipulating their primary sex ratio. We examined the sex and hatching order of nestling bald eagles (Haliaeetus leucocephalus) over 17 years on one lake and 5 years on another. The lakes are approximately the same size, but differ dramatically in eagle density and prey abundance. In years when the number of eaglets fledged was high (suggesting higher food abundance), there was a significant bias in the first-hatched chick toward the larger sex (females), and broods with a first-hatched male and a second-hatched female (MF broods) were under-represented. In years with lower productivity, and on the lake with lower food abundance, there was a male-bias in the population sex ratio of nestlings and the first-hatched egg. Variation in sex ratio and hatching order may relate to the probability of siblicide associated with MF broods, or the differential cost of raising the sexes.
Bortolotti, Gary R. 1986. Influence of Sibling Competition on Nestling Sex Ratios of Sexually Dimorphic Birds. The American Naturalist 127:495-507.
Theoretically, the ratio of male to female offspring should equal the inverse ratio of the cost of their rearing. For birds exhibiting brood reduction, the cost of raising offspring sexually dimorphic in size may not be independent of the sex composition of the brood if males and females are not equally affected by sibling competition or are not equally effective at competing with a sibling of the opposite sex. Parents may thus manipulate the sex ratio of their brood to achieve an optimal combination of the sexes and to maximize their fitness. By examining the effects of sex, growth, and hatching asynchrony on the relative size of sibling bald eagles, I show that the probability of brood reduction is not equal among broods of different sex composition. The hatching sequence of male first and female second was predicted to have the greatest chance of experiencing nestling mortality. This type of brood is rare in bald eagles because there is a sex-dependent hatching sequence whereby the first egg in mixed-sex clutches is predominantly female (93%). In contrast, golden eagle broods of female first and male second appear to be the combination most likely to result in brood reduction. Golden eagles do not adjust their prenatal sex ratio, but there is a postnatal sex bias in favor of females caused by brood reduction in years of poor food availability.
Bortolotti, Gary R. 1986. Evolution of Growth Rates in Eagles: Sibling Competition vs. Energy Considerations. Ecology 67:182-194.
Nestlings of birds that raise only one young (B1 species) grow slower than those of birds that raise more than one young (B2 species). B2 species may be fast growing because sibling competition exerts a strong selective force for rapid growth. Other hypothesis have been proposed to explain the slow growth of B1's. To overcome the problem inherent in previous investigations of comparing species widely divergent in ecology and phylogeny, I analyzed patterns of variation in growth of one group only: eagles of the world. I fitted growth curves to data obtained from the literature for some species, but most eagles were compared using the length of the nestlings period as an indicator of growth rate. I also collected data on the growth of wild Bald Eagle (Haliaeetus leucocephalus) nestlings. I investigated how postnatal growth may be related to brood size, clutch size, nestlings mortality, body size, and prenatal growth. B1 eagles were found to grow slower than B2 eagles. Differences in foraging ecology, diet, and mode of development are unlikely to account for the observed variability in the rate and form of growth. Contrary to the sibling competition hypothesis, growth rate was not correlated with intensity of sibling competition. Eagles that regularly lay two eggs but always lose one chick because of sibling competition (obligate fratricide) grow slower than those species in which such mortality may or may not occur (facultative fratricide). Species characterized by facultative fratricide grow at a rate expected for their adult body size, whereas to B1 species do not. B1 eagles are characterized by growth curves with early inflection points compared to B2 eagles. The shape of the growth curves and slower growth rates of B1 species and contrary to predictions of the sibling competition hypothesis and may instead have resulted from selection to reduce peak energy requirements of the nestlings. I present a model of the effect of hatching interval, species-specific growth rate, and relative growth of siblings, on the probability of fratricide, which suggests that sibling competition is not an important factor in selecting for rapid growth.
Simmons, Robert. 1988. Offspring Quality and the Evolution of Canism. Ibis 130:339-357.
Obligate siblicide, known as 'cainism' in large raptors, is a taxonomically widespread avian phenomenon that remains inexplicable as a simple consequence of food stress: two young can be raised to independence in experimentally manipulated nests, and food supplements do not decrease sibling aggression.
A review of the Falconiformes identified 23 species in which obligate and facultative cainism is regular. All species have small clutches and deferred acquisition of adult plumage. Obligate cainists in particular are large, long-lived species characterized by extreme subadult mortality and intense competition for breeding sites. Hence, it can be suggested that early sibling conflict, in the absence of food stress, is the end result of selection for quality (survival) and competitive ability. Cain's domination or killing of Abel insures (1) an increase in Cain's chances of survival through the high-risk, pre-breeding period via improved nestling weight gain, and/or (2) domination of surviving sibs, enhancing Cain's competitive abilities and thereby increasing the probability of achieving breeding status. Only among long-lived species can the benefits of enhanced survival and competitive ability outweigh the major costs of sibling loss.
Facultative cainists, which in more than 10% of cases raise more than one young (despite aggression and sibling hierarchies), not only lay larger, more variable clutches, but on average attain adult plumage earlier than obligate cainists. Their shorter lives and higher population turnovers are consistent with their less extreme siblicidal tendencies. Similar life-history traits and cainistic habits in other avian orders parallel those in the Falconiformes, indicating several independent evolutionary pathways to cainism.
Retention of the second egg by obligate cainists, usually explained as insurance against failure, may instead allow parents adaptively to track population stability. Thus when breeding places are numerous (habitat saturation and competition low), parents laying two eggs and rearing two young may achieve greater fitness than single-young parents. When populations become saturated (competition high), selection should favour high-quality, competitive young and levels of siblicide should increase. A proximate mechanism is proposed linking population saturation with the incidence of cainism, based on demonstrable population characteristics found in several long-lived species.
Markham, Catherine, and Bryan D. Watts. 2007. Documentation of Infanticide and Cannibalism in Bald Eagles. Journal of Raptor Research 41:41-44.
Although unrelated individuals infanticide and cannibalism are well documented for several bird species, direct observations of this behavior in birds of prey are relatively scarce. We describe a case of infanticide and cannibalism in Haliaeetus leucocephalus . In this case, the adult resident male disappeared shortly after the chick hatched, and the female assumed the responsibilities of parenting without help until the nest failed. The first instance of cannibalism took place when the youngest of the three chicks died and was given as food to his brothers by the mother. Other acts of cannibalism occurred after the Occurrence of infanticide, when a male four years of age entered the nest by killing and eating the two remaining chicks. We suggest that these events of infanticide and cannibalism were closely linked to the disappearance of the resident male, and potentially related to the replacement of the male by the individual of four years.
Edwards, T.C. and M.W. Collopy. 1983. Obligate and Facultative Brood Reduction in Eagles: An Examination of Factors that Influence Fratricide. Auk 100:630-635.
Fratricide in eagles (Accipitridae: Accipitrinae) is either obligate [second hatched nestling (C2) always dies] or facultative (C2 occasionally dies) and appears to be a function of relative size differences between siblings. Several factors, including time between hatching, differences in hatching weights, and possibly the sex of the nestling in conjunction with its hatching sequence, influence size difference. Size differences are modified further by feeding rates of young by adults. These factors determine the relative differences in locomotor development and coordination and thus the ability of the first-hatched nestling to control access to and monopolize parent-provided resources. Significantly greater (P < 0.0001) within-clutch volume differences (an indicator of disparity in hatching weight) and greater time between hatching (mode of 3 versus 2 days) are found in eagles in which fratricide is obligate (three species) than in those in which fratricide is facultative (eight species). We suggest that these differences are proximate mechanisms that account for observed differences in the frequency of fratricide in eagles. Although size difference is determined in part by the sex and hatching sequence of the nestling, the role of offspring sex in fractricide is not clear.
21 February 2012 (Sequoyah): During the early stages of life after the chicks hatch out of the eggs, the adult female spends most of her time brooding the chicks so they are kept warm. She also defends them from nest predators such as crows or mammals like raccoons. The male's job is to bring in food to the nest, and usually a large surplus builds up in the nest as the young hatchlings don't consume much at this stage. The male also fills in to brood young chicks when the female gets up to defecate, to eat, and to take a break. As the chicks continue to grow, the food demands increase significantly. In fact, they increase so much that the male spends nearly all his time hunting, and thus is gone from the nest while the female stays at or near the nest to protect and brood the still developing young. As the youngsters continue to grow, their demands for even more food increase, and eventually it is necessary for the female to hunt so that enough food can be provided for the ever growing family. During this time, a "runt," as is found in this nest, might have great difficulty competing with its larger siblings for food and may succumb to starvation or to siblicide. It is also during this time when both parents may be absent from the nest at the same time while hunting that the large but still undeveloped young are most vulnerable to serious predators such as bobcats or other large raptors.
14 February 2012 (Sequoyah): After a modest winter storm including some snow and freezing rain, and extended days of overcast weather, the cameras are struggling to get enough solar energy to remain on. We do expect them to start working better again today as the weather improves.
9 February 2012 (Sequoyah): The three chicks range from 11 to 16 days old today, and it is interesting to observe their behavior in the nest with regard to thermoregulation. They are all covered with the very light colored first down at this time. If you look closely, however, the darker grey, second down is just starting to barely peek through on the oldest chick, and it will progress rapidly from this point. If winds are calm, even in cold (40F) weather, the chicks can be left with no or only partial brooding by the adult. By lying clumped together they reduce the amount of exposed surface area from which they lose heat. Naturally, the smallest ones need more heat and might seek a central position in the pile. If temperatures really drop, however, and keeping warm is at a premium, the larger chicks will muscle their way under the adult and next to their siblings, and a weaker chick will lose out in the competition to keep warm; usually, however, the adult will brood the chicks adequately. There are times when a small, weak chick can get caught in the middle of a brood and even fatally overheat owing to an inability to work its way out of a "hot spot."
If too cool, the chicks will complain vocally, and their mother will waddle onto them to brood, providing heat and reducing exposed surface area. This is especially necessary when temperatures are cold and windy. The chicks' own body heat production actually changes with feeding bouts. Assuming ambient temperatures are moderate, when the young of this age have empty crops they will sit tightly huddled together, keeping their wings and legs close to their bodies, conserving heat by reducing surface exposure. If they have just been fed and have full crops, they are producing plenty of heat, and you will note that, especially the older ones, will lie there rather spread out, perhaps avoiding sibling contact, with an extended leg and extended necks, exposing more surface area in order to dissipate heat. As the chicks grow, their self heat production increases, gradually decreasing their need for brooding by the adults and for contact with siblings. Still, they might lie close together, preening their growing feathers, and sometimes preening (allopreening) their nest mates as well.
3 February 2012 (Sequoyah): With regard to adult eagles' feeding of chicks, you may or may not have noticed precisely how the act of transferring food from the adult to the tiny chicks occurs. The adult tears off a tiny morsel of fish/meat and holds it in the end of its beak with the upper and lower mandibles just slightly apart, saline dripping as described in yesterday's post. The adult never approaches the chick face to face with symmetrical alignment. Instead, the adult turns its head about ninety degrees to the side, allowing the chick to then grasp the morsel by "scissoring" the tips of its mandibles along the (now) vertical slot formed by the small gap between the adult's upper and lower mandibles, allowing easy access to the food by the chick.
You might also notice that when the adult prepares to brood the chicks, the adult walks slowly around the chicks and "balls up" its feet so that the sharp talons are not exposed. As the adult gently slips its "balled up" feet in around or among the individual chicks, it is careful to avoid each baby. The single, central brood patch where down and body feathers have dropped out of the adult's belly (in contrast to the two separate brood patches present on falcons) allows direct contact by eggs or chicks to warmth provided by the adult's skin. Capillaries near the skin's surface carry heat from circulating blood, very similar to the operation of a radiator. The loose down that is on the body of the chick helps it squirm around under the parent and find a microclimate where the chick is comfortable, regardless of current weather conditions. On warm days you may notice heads pop out from under the adult in an effort to cool down when the chicks are becoming too warm.
2 February 2012 (Sequoyah): Nasal glands in the anterior part of the eagle skull produce a saline solution that runs from the nares or nostrils of the feeding adult and down the beak to drip off its tip and onto the small bits of meat fed to the chicks. This keeps the sticky fish flesh moist and makes it easier for the chicks to swallow. There is speculation over whether such secretions include some type of disease resistant content or antibodies, as does colostrum in mammalian breast milk or has been shown for the saliva of swifts, but preliminary studies in falcons have concluded only saline is present. To see the saline dripping off the adult beak is difficult, even in person, but close observation might allow sharp-eyed, lucky, camera watchers to witness this phenomenon in some circumstances.
1 February 2012 (Sequoyah): As viewers already know, Sequoyah National Wildlife Refuge bald eagle egg# 1 was laid Dec 17, #2 followed on Dec 20, and #3 was laid Dec 23-24. The hatching of egg #1 on Jan 24, #2 on Jan 25-26, and #3 on Jan 29 was the result of the eagle's incubation process that started with the appearance of the second egg, at least to some degree (see below), rather than waiting until all eggs were laid before incubation commenced. (In the latter case, all eggs would hatch at the same time.)
Although the eagle's full incubation temperature is about 99.5F, keeping the eggs partially warm (well below 99.5F) during cold weather when they are laid, is necessary to keep each egg from freezing following its expulsion from the hen; freezing of eggs can happen usually in the mid to low 20's F. The female eagle prevents freezing by squatting over them, but does not go into full incubation posture (indicated by the contour feathers on her back being erect) with the eggs in full contact with her brood patch. Even while warmed at less than full incubation temperature, the embryos in the eggs will begin to develop during the first few days once laid. If full incubating temperature (99.5F) is not applied within about a week, the developing embryos die.
Determining exact incubation periods with precise hatching dates for birds can be somewhat difficult, especially during extremely cold weather when parents are on the nest continually (without rising) or when hatching occurs during night time. Bald eagles incubate for about 35 days before the chick breaks through with its egg tooth and lifts up a small portion of the shell, a process called pipping that allows the youngster to breath outside air for the first time. The chick will stay inside the shell and rest, following pip, for about 36-72 hours. Then it begins to rotate inside while cutting the shell in half with its egg tooth, a small projection on the top of the upper beak. The turning process varies in length of time to complete, but it usually takes between one half to two hours. Often, the incubating female will rise slightly and readjust herself when she feels the movements of the chick. The full incubation period will last approximately 35 days as exhibited by the time periods between laying dates and hatching dates recorded above. Some variation in development (age of chick inside the egg), however, can be a product of the difficulty in knowing exactly when full temperature incubation begins for each egg, and variation in position of egg (and its contact with brood patch) as it is tumbled about during incubation under the adult.
Since the embryos begin to develop when the adult female is warming the eggs, even though not fully incubating, staggered hatching of the chicks will result. This gives the first hatched chick a distinct advantage, with as much as five days growth over the third chick that has just hatched. While that seems minor, the first chick can consume a great deal of food during those early days, sometimes weighing nearly twice as much as the third chick at hatching. This allows the first chick to overpower the third chick, and even the second chick when competing for food from the feeding adult. Eventually as they grow, the third chick often continually loses out, getting little or no food during prey deliveries and feeding bouts from the parent. Plus, bald and some other eagle chicks have a tendency to commit siblicide when competing with fellow nest mates. This is thought to be a way of allowing for survival of the strongest chicks during periods of unpredictable food supplies. It is also true that many second and even third chick bald eagle nests fledge all the young, and a few instances of four young fledging from one nest have been recorded. We can watch the development of the chicks in this nest and see how they progress. Remember, we are only eavesdropping on their nest life and will not interfere with the progress of the eagles' natural reproduction and growth.
29 January 2012 (Sequoyah): The third chick hatched this afternoon!
26 January 2012 (Sequoyah): There are now two chicks in the nest!
24 January 2012 (Sequoyah): The first eaglet has hatched!
23/24 December 2011 (Sequoyah): A third egg was laid.
21 December 2011: We plan to replace some hardware in the next few weeks that should improve the reliability of the Sooner Lake video.
20 December 2011: A second egg was laid in the Sequoyah nest.
17 December 2011: A first egg has been laid in the Sequoyah nest.
We have equipped two young Bald Eagles with satellite transmitters so we can follow their movements after fledging. Visit our tracking page at http://www.suttoncenter.org/pages/eagle_tracking or use the link to the left.