Who’s Living Inside That Osprey Nest?
Volume 2 Issue 6
Pam Narney firstname.lastname@example.org
Many years ago, when the Colonial Beach Osprey Festival was just beginning, I was walking with a friend on the boardwalk. She saw a bird fly out of an Osprey nest and said, “There’s an Osprey!!
I thought, we have a long way to go here. What she saw was a sparrow.
There is little scientific literature about non-Ospreys living under occupied Osprey nests.
One writer in Ohio said, “There is no such thing. We haven’t seen that.” But remember Aristotle: “Seeing is believing”.
Let’s call these birds, who breed but do not build the nest, co-nesters.
To Osprey observers, these little birds are a mystery. Why do they nest there? Why don’t Osprey, who aggressively protect their nests, chase them away?
Many Virginians notice house sparrows darting in and out of the bottoms of Osprey nests. This behavior is common on Virginia’s Eastern Shore and in the Colonial Beach area.
Scientists believe that breeding sparrows get protection from predators, a phenomenon called “protective nesting”. The smaller birds might alert Osprey to predators the Osprey missed (Ewins).
My observations show that the Osprey pay no attention to the sparrows. A small bird around its nest must not be perceived as a threat to the Osprey. Both families go about their lives peacefully.
This is called commensalism: a symbiotic relationship where one benefits and the other is unaffected. Small birds may warn larger birds about predators. This may be an urban myth. There is little documentation to support this partnership. If the smaller birds alert Osprey to predators then the relationship is symbiotic mutualism.
In Florida, Green Quaker (Monk) parakeets live and breed in Osprey nests. Osprey build large stick nests which attract smaller birds that also build stick nests. These non-native parakeets build stick nests and favor Osprey locations: silos, utility poles and trees. They benefit from existing nests and protection from predators.
However, parakeets and other birds who use Osprey nests might bring more parasites to the nest.
If this proves true, the relationship changes to one where one species benefits and the other is harmed.
Other stick nest builders
Scattered reports reveal that other birds breed within Osprey nests (Ewins). Research in the Great Lakes basin found three species, plus house sparrows within occupied Osprey nests:
and the European starling.
Most of these birds build stick nests or nest in cavities, so the Osprey nest is attractive and familiar.
Canada geese squatters
Unoccupied Osprey nests attract birds ready to breed. They benefit from existing Osprey nests while harming Ospreys. Squatters, who inhabit and breed in existing Osprey nests, are becoming more common.
The most frequent reports of birds in Osprey nests were Canada geese (Ewins). When Canada geese or other birds try to take over a nest when Osprey are in residence, Osprey aggressively and successfully chase them away. But when the geese get to the nests first, the dynamic changes.In the Colonial Beach area, Canada geese have taken over Osprey nests. They breed before Osprey. When geese occupy the nest before Osprey arrive from migration, they stay until the eggs hatch forcing the Osprey to wait to mate and lay eggs.
Osprey who return to find their nests inhabited cannot seem to force the geese out. Some may find other nest sites and rebuild. Others have to wait for the geese to leave. Osprey did nest in other spots, “but more often the Osprey pair occupied the platform once the goose clutch hatched, although none of the pairs laid eggs in that same year” (Ewins).
Osprey are faithful to their nesting sites. We assume that Ospreys spent time trying to move the geese out, further delaying breeding and risking the successful birth and development of healthy chicks.
Ewins and his observers also found a few reports of great blue herons, bald eagles, red-tailed hawks, great horned owls, and other larger birds breeding in Osprey nests.
What other birds have you seen in or near Osprey nests? How do they behave? Email me. I will add your observations to our local Colonial Beach observations.
Thanks to Sally Adams for the idea for this blog.
Cornell Bird cam, Savannah, GA. Jan 26, 2017.
Ewins, Peter J. et al. “Birds breeding in or beneath Osprey nests in the Great Lakes basin.” Wilson Bulletin. 106(4), 1994, pp. 743-749.
This blog has excellent pictures of sparrows in Osprey nests.