Charlie Todd

Encounters between boaters and bald eagles are on the rise along the entire Maine Island Trail in all seasons. For most, viewing an eagle is both enjoyable and a reminder of the vulnerability of our natural resources. In 1978, bald eagles were listed as an Endangered Species in Maine and 42 other states. Following decades of special attention, their status was downgraded to that of a Threatened Species in 1995. Legal protection, population monitoring, and habitat management are priorities with either classification.

Thanks to continued progress, eagle recovery is nearly complete. “Delisting” (removal of the Threatened Species designation) is imminent. In Maine, the breeding population has risen from a low of only 21 nesting pairs in 1967 to an impressive tally of 412 nesting pairs of bald eagles in 2006. Thirty years ago, only easternmost Washington County had viable eagle numbers, but bald eagles now reside in all Maine counties. Downeast waters between Penobscot Bay and the New Brunswick border have the highest nesting density of eagles along the Atlantic seaboard between major strongholds in Cape Breton Island, Nova Scotia and the Chesapeake Bay region of Maryland and Virginia.

How do eagles fare from increasing human encounters? The details matter. Reactions vary among individual eagles, specific eagle habitats, and between seasons. An eagle near its nest will respond more during sensitive phases of the breeding season in spring than later in summer. Encounters in the fall may not affect the same bird at the same locale. Young eagles still learning flight and survival skills after nest departures in mid-summer are especially easy to approach but are particularly vulnerable to disturbance.

As visitors to the Maine Island Trail, we can enjoy wildlife more and impact them less by understanding their biology and needs. Good stewardship is crucial to a lasting species recovery. If you recognize the body language of a disturbed eagle, you can remedy the situation by altering your location and behavior. Those adjustments may prevent future encounters that result in eagles leaving as you arrive. Repeated disturbances may discourage eagles to abandon an area altogether.


Natural history

An adult bald eagle is readily recognized. The white head and tail feathers are a sharp contrast to its dark brown – blackish body plumage. Adult plumage is attained in the fifth year of life and (except for minor blemishes) is unchanged. The longevity record for eagles in the wild is 28 years. Adult eagles in coastal Maine are not migratory. They can be seen near a nest every month of the year, but have the flexibility to wander regionally when not guarding eggs or nestlings during the breeding season.

Subadults (aka, immatures or young eagles) are mostly dark brown, but individual feathers are variably mottled with white. They are not smaller! First year eagles (= eaglet, fledgling or juvenile) are full grown when they first leave the nest; their feathers, beak, and eye color are nearly black. Over the next 4 years, the head plumage gets progressively whiter, the beak color gradually becomes bright yellow, and the eye color changes to pale golden. Eagles less than 5 years old can wander great distances. Young eagles from Maine have been seen from Nova Scotia to South Carolina and west to Ohio. Subadults wintering Maine have come from as far away as Michigan and Saskatchewan. Migration routes and wintering areas are used habitually by individual eagles.

Eagles usually pair for life. Nests are built in prominent trees near shorelines. Adjacent waters and tidal flats are preferred feeding areas for fish, seabirds, waterfowl, etc. Eagles on the mainland usually construct a nest 10 – 30 feet below the canopy of a tall pine, but those on offshore islands may be at the very top of spruce trees: very similar to that of an osprey. In fact, the two species regularly compete for nests and fish. Eagles add sticks to their nests are each year. A sturdy tree may support a nest used by generations of nesting eagles. Nests can vary in size from 3 to 7 feet in diameter and up to 20 feet tall!

If they have strayed at all, eagles resume a steadfast watch over nests in coastal Maine during February or early March. The sensitive period has begun. One to 3 eggs are laid by early April; the timing can vary by as much as 6 weeks at neighboring nests. Vulnerability to disturbance peaks as the adults alternate non-stop care of eggs during 5 weeks of incubation. An incubating eagle sits so tightly on eggs that it is rarely seen from the ground on nearby waters. Make no assumptions about apparently empty nests!

Intrusions that render the eggs exposed for as little as 10 minutes on a cool, damp day in April can cause nesting failure. Hatching occurs by early-May. The adults brood young, downy chicks closely for several more weeks to guard them from precipitation, thermal stress, predators, etc. Eaglets grow from 2 ounces at birth to full size (10 – 13 pounds) before departing the nest as 3-month old fledglings. This remarkable growth is possible only by multiple food deliveries each day. Adults displaced from favor foraging areas may have difficulty meeting this challenge.

Adults spend less time at nests as fledging approaches. However, privacy at nests remains critical to avoid forcing eaglets to attempt first flights prematurely: an event that can result in death, injury, exposure to predators, etc. Young eagles on-the-wing develop slowly and are fed, guarded, and trained by parents for another 3 months. Their survival skills are enhanced if intrusions that disrupt the process are minimized. The nest remains a focal point through the remainder of the summer and early fall until fledglings disperse, but at least the birds have mobility to leave if disturbed during this phase.


Tips for coexisting with eagles

1. Avoid this flawed scenario: “Look, the eagles are putting on a show for us!” If you see 1 or (especially) both adults repeatedly circling an area, flapping hard rather than soaring, and vocalizing … move away quietly. You may be too close to an active nest or a fledgling that requires parental attention.
2. Disturbance thresholds vary. Eagles may leave a perch or nest if approached within 1500 yards. You may not yet see it. Do not assume that you can land and walk near an eagle just because it has not reacted to boat traffic. Boat landings and activity on shore usually disturb eagles at 2 – 3 times distances tolerated of passing boats.
3. Eagles have adapted somewhat to boat traffic. Fishing boats or those cruising past by motor or sail usually pass more quickly than kayaks. If you are paddling near an eagle, avoid steering directly at it and pass quietly. You may be rewarded with a prolonged view. Shifts in posture or wing flapping on the perch are signs of nervousness. Do not intentionally anchor or linger within sight of nests.
4. Avoid approaching an eagle down on the ground, shore, tidal flat, or ledge. It may be feeding or reluctant to fly because of inexperience or injury. Watch from a safe disturbance and report any suspected problems. Note the location, time, whether the eagle appears wet (only a temporary deterrent to flight), if wing are ajar or feather tips are dragging on the ground, suspicions of entanglement in fishing gear, etc.
5. Ospreys, crows, and many smaller birds may fly repeatedly at perched or flying eagles in an attempt to make a potential threat (= the eagle) go away. If an eagle stays despite this mobbing behavior, it really wants to be in this area. Proceed carefully.
6. If you are boating in late-winter or spring, remember that nesting eagles are much more sensitive to disturbances than later in summer.
7. MITA has attempted to avoid sensitive eagle locations. Nests not on the trail are not described in the guidebook, but we welcome your observations of such locations. Eagles are most nervous and vulnerable to intrusions near nests.
8. Eagles are notoriously selective of nest locations, feeding areas, and even perch trees. The real test is seeing them in traditional settings. An encounter that becomes familiar as you boat through a locality is especially rewarding and proof positive that your use is compatible with the special needs of bald eagles.