Avoid Disturbing Bald Eagles
Bald Eagles were a common North American bird in the 1700s. However, by the mid-20th century they were are in the lower 48 states and extirpated from Connecticut. While loss of habitat and illegal shooting were factors in the decline of the species, the scientific consensus is that pesticide poisoning, especially with DDT, was the main factor. Top predators like the Bald Eagle – and the Osprey – are susceptible to such poisoning because the fish they eat concentrated DDT along the food chain and caused the eggs laid by the females to have shells that were weakened and easily broken during incubation. Following the banning of DDT in the US in 1972 Bald Eagles began to rebound and in 1992 the first confirmed nest site in Connecticut since the 1950s was recorded in Litchfield County. Five years later an additional pair successfully nested and in the following 20 years nesting Bald Eagles have spread throughout the state.
In fact, they have made a such strong come-back in that they have started nesting in populated areas. In south-central Connecticut an eagle pair has been nesting for several years not far from Route 5 in Hamden. Other pairs in Guilford and New Haven are in other high traffic and relatively high visibility sites.
While it appears that Bald Eagles have become somewhat accustomed to humans, they are still susceptible to human disturbance, especially during the crucial nesting period and during winter when food is harder to come by.
In Connecticut the Bald Eagle breeding period generally begins in January with courtship and nest building. In late February or early March egg laying begins with a clutch of two to three eggs, followed by five weeks of incubation. After the eggs hatch the eaglets are fed by their parents until at 10-13 weeks they are able to take their first flights. For another six weeks the fledgling Bald Eagles are dependent on their parents for food while they gain flight experience and learn to find food themselves. From start to finish the breeding cycle lasts six to seven months.
Bald Eagles are protected by two federal laws, the Bald Eagle and Golden Eagle Protection Act of 1940 and the Migratory Bird Treaty Act of 1918. Connecticut General Statue 26-93 prohibits disturbing a Bald Eagle. Violations of these laws can result in fines and/or imprisonment.
The tables and information below are adapted from the USFWS Midwest Bald Eagle page.
The Bald Eagle breeding cycle in Connecticut begins in mid-winter and extends into early fall. During this time Bald Eagles spend their time at their nest site and are sensitive to human disturbance. After the young fledge the parents continue to feed them in the nest area. After a short time the feeding can take place away from the nest before the young are left on their own. From early fall to mid-winter the adults birds disperse and the nest site is not regularly occupied as it is during nesting.
|Nest Building >>|
|Egg Laying/Incubation >|
|Hatching/Rearing Young >>>>>|
|Fledging Young >>|
Bald Eagles sensitivity to human disturbance during the nesting period varies slightly depending on the stage and the birds’ reaction can vary from abandoning the nest site, failure to lay eggs, leaving eggs during incubation resulting in failure to hatch, reluctance to feed growing chicks, and scaring young birds into leaving the nest before they are fledged.
|Phase||Activity||Sensitivity to Human Activity||Comments|
|Courtship and Nest Building||Most sensitive period; likely to respond negatively||Most critical time period. Disturbance is manifested in nest abandonment. Bald eagles in newly established territories are more prone to abandon nest sites.|
|Egg laying||Very sensitive period||Human activity of even limited duration may cause nest desertion and abandonment of territory for the nesting season.|
|Incubation and Hatching||Very sensitive period||Adults are less likely to abandon the nest near and after hatching. However, flushed adults leave eggs and young unattended; eggs are susceptible to cooling, loss of moisture, overheating, and predation; young are vulnerable to elements.|
|Nestling period, 4 to 8 weeks||Moderately sensitive period||Likelihood of nest abandonment and vulnerability of the nestlings to elements gradually decreases. However, nestlings may miss feedings, which may affect their survival, or may prematurely leave the nest due to disruption,|
|Nestlings 8 weeks through fledging||Very sensitive period||Gaining flight capability, nestlings 8 weeks and older may flush from the nest prematurely due to disruption and die.|
Bald Eagles may respond in a variety ways when they are disturbed by human activities. Prolonged absences of adults from their nests can jeopardize eggs or young. Depending on weather conditions, eggs may overheat or cool and fail to hatch.Young nestlings rely on their parents to provide warmth or shade, and may die from hypothermia or heat stress if adults are forced away from the nest for an extended period of time. Eggs and juveniles are subject to greater predation risk while they are unattended.
If human activities disrupt the adults’ foraging and feeding schedule, the young may not develop healthy plumage, which can affect their ability to survive.
Older nestlings may be startled by loud or intrusive human activities and prematurely jump from the nest before they are able to fly or care for themselves.
Human activities that cause any of these responses and lead to injury, a decrease in productivity, or nest abandonment could be, considered disturbance under the Eagle Act and thus a violation of the Act.
Photos: top, middle: Martin Torresquintero, bottom: USFWS