Blog #458 Mixed-Use Housing

 

Tree Swallows living in the bottom of an Osprey nest in Idaho, courtesy of Karen Balch.

Ever notice the small birds coming and going around large Osprey nests? At first it seems disconcerting to see prey so close to this mighty bird of prey, but the little birds are safe. Ospreys are obligate fish-eaters; birds have nothing to worry about.

The sloppy stick Osprey nests can get as big—sometimes as tall as 10 feet—and frequently, house smaller breeding birds in or beneath active Osprey nests. During

A tall Osprey nest built on a cliff in Italy, courtesy of Quora.

the spring, the Salt Point Osprey nest usually has a house sparrow nesting in its base.

Besides house sparrows, cavity-nesting common grackles, tree swallows, and European starlings are often noted within Osprey nests. These cohabitations are peaceful with no agonistic interactions. Interestingly, in areas with Ospreys nesting in trees, more of these smaller cavity nesters are seen “cohabitating” with Ospreys than when nests are on artificial platforms. Several studies found Osprey nests grew larger in trees than on artificial substrates and housed more of these small birds because of the additional space available. However, many artificial nest substrates are stronger and do not topple as readily as the nests in fragile older trees.

Ospreys readily attack potential predators near their nests, such as crows, other raptors, and mammals. It is thought these cavity nesters breed in Osprey nests for their protection. The phenomenon where "weaker" bird species nest in or around the nests of birds of prey, like Ospreys, is known as "protective nesting.”

However, there are also mutualistic aspects to this partnership. As in many species, adult Ospreys are alerted and respond to alarm calls of other bird species near their nest and may benefit from such nesting associations. Snakes crawling up to the nest may go undetected by the Ospreys, but a small bird breeding beneath or in the nest would get alarmed and send out a warning chirps

Observers have long wondered if small birds actively select Osprey nest sites because of their additional protection, or simply because of their availability when nesting cavities are at a premium. Small birds may also benefit from an increased availability of nest material and insect food. Tree swallows collect down and feathers from and around Osprey nests to line their nests. Both barn and tree swallows catch the flying insects attracted to the smell of fish remains in the nests.

At least 12 more species of cavity-nesting birds are found associated with Ospreys, including the northern flicker, Lewis' woodpecker, western kingbird, violet-green swallow, short-toed treecreeper, white wagtail, and a shrike (species). One historical account (Abbott, 1911) recorded 6–7 pairs of common grackles breeding in the base of a single Osprey nest. This same author reported a nest of meadow mice living in the base of an Osprey nest.

An unoccupied Osprey nest is inviting to other breeding birds as well. Eleven larger bird species have been recorded nesting in or beneath Osprey nests such as the black-crowned night-heron, green heron, great blue heron, Canada goose, mallard, American black duck, bald eagle, Peregrine falcon, barn owl, and great horned owl.

Canada goose usurping Osprey nesting platform, courtesy of Rachel Ecols.

Ospreys sometimes take over unoccupied bald eagle nests, but, if they are challenged, the dominant eagle prevails. Among non-passerine species, Canada Geese have been reported nesting in Osprey nests most frequently. Mortality of goslings jumping from high Osprey nests is very low. Presumably such sites are attractive to geese owing to a reduced risk of predation. Osprey platforms on Portland Point Road and at Salt Point on Salmon Creek have been usurped by Canada Geese for the last several years. The geese are sitting on eggs when the Ospreys’ return to this area and are difficult to budge from their nests, reducing the nest site availability for Ospreys.

Eyes to the sky!

Candace

Candace E. Cornell

Friends of Salt Point, Lansing, NY

Cayuga Lake Osprey Network cec222@gmail.com

 

EYES ON OSPREYS

WATCH!

Salt Point Osprey Nest Cam 2022-23

READ!

 On Osprey Time: Ospreys of the Finger Lakes

VISIT!

Cayuga Lake Osprey Trail Nests Driving Tour

Complete Cayuga Lake Osprey Trail

HELP PROTECT OSPREYS:

•Stay 300 feet away from nests during the breeding season.

If the Osprey vocalizes, you are too close! BACK OFF IMMEDIATELY.

•Carry binoculars to view wildlife from afar.

•Recycle used fishing lines, twine, and nets, which can kill Osprey.

•Join the Cayuga Osprey Network: cec222@gmail.com.

•Help keep local waters clean, healthy, and safe. Pick up trash and do not litter. Trash stays in the ecosystem a long time before it disintegrates. Plastic just breaks down into smaller pieces.

Aluminum Can-------------------80 to 100 years

Plastic 6-pack Holder----------100 years

Orange or Banana Peel-------Up to 2 years

Plastic Film Container---------20 to 30 years

Plastic Bags----------------------10 to 20 years

Glass Bottles---------------------1,000,000 years

Plastic Coated Paper----------5 years

Nylon Fabric---------------------30 to 40 years

Leather----------------------------1 to 5 years

Wool Socks----------------------1 to 5 years

Tin Cans--------------------------50 years

    Source: NYSDEC