Many of my favorite memories of spring involve watching "old friends" return from their wintering grounds, and setting up housekeeping to establish their local families. The return of these species mark time for me -- the date when I expect to see the returning tree swallows, hear the first grouse drumming, and enjoy the tik-tik-tik of the Virginia Rail. And certainly on that list has to be the return of the master fisherman - the Osprey.
Osprey are conspicuous birds and fun to watch, and recently, I enjoyed some time with this industrious returning pair. Osprey nests are amongst the largest bird nests known - with long established nests reaching 3-6 feet in diameter and up to 13 feet deep! They will typically reuse a nest site over many years, improving it with each season. The male returns well before the female, and will claim the nest site immediately. He is also almost solely responsible for building the nest, bringing materials for the female to accept or reject - and then she will use them to form and line the nest. The thickest material is placed on the bottom of the platform, with materials getting thinner and shorter as they go up. The top of the nest is a cup lined with fine nesting material that includes grasses, seaweed, moss, and pieces of plastic, cardboard, fabric, and other materials that the nesting pair considers adequate soft material to line the center area where eggs are laid.
This male returned repeatedly with bits of trash, including bait bags, fish nets, and even a fast food take out bag. Some of the presented items were accepted by the female and incorporated into the nest. Others, however, were rejected. If she didn't like something the male brought, she would wait until he went off for more, and then would toss it over the rim of the nest. The ground below was littered with a colorful array of trash, grasses, and broken bits of sticks.
At one point, the pair felt unabashedly amorous, despite the presence of a photographer nearby. Osprey usually mate for life, and are generally monogamous - although polygyny does occur where one male will breed with 2 females. As a rule, however, the "second" nest does not fare as well as the original nest, as the male prioritizes which young he provides care for - and he alone generally provides the fish for the female and young. Osprey will mate quite often, and begin while they construct the nest. They will mate between 88 and 338 times before they start to lay eggs! As you can see above, this is a tricky and difficult maneuver as the male must "hover" on top of the female, attempting to make cloacal contact. Some of these mating attempts may be "practice runs". However, as the female gets closer to egg-laying, she becomes more receptive and the male stays close to ensure paternity. She will lay a total of 1-4 eggs (more when food is abundant) every other day until the entire clutch is laid. Most females will start to incubate the eggs after the second one is laid - and because of this, the young hatch asynchronously (at staggered times). This means that the first born have a distinct advantage - sometimes being twice the size of their siblings when they hatch several days later.
If you ever wondered what a bird cloaca looked like after you had read about "cloacal kisses" during mating -- anatomy alert! It is visible on the above photo, although discretely covered by a wing feather, you can still make out the basic structure, which is somewhat reminesent of a belly button....... Look in the white area on the female (lower bird) below the barred tail -- and slightly covered by a right wing feather.
After mating, the male immediately went back to finding what he felt was suitable nesting materials, and presenting them to his mate. The female spends most of her time in the nest, protecting it (and eventually her eggs) from other osprey, as well as predators such as Great-horned owls, raccoons, Bald Eagles, and crows. At night, before the eggs are laid, many osprey choose to sleep in nearby trees and leave the nest. However, once the eggs are laid, the female does the majority of the incubation and remains in the nest at almost all times. The male protects the nest and delivers food.
At one point, the male left and came back with empty talons. Mom certainly did not appear very impressed with this lack of effort! Guys, how many of you have seen exactly this look? I find osprey to be uniquely expressive birds.
At one point, another osprey approached the nest - and it is clear how extremely attentive the pair became. In areas of rich food sources nests can be clustered close together - sometimes, even in the same tree. However, in many circumstances, they may be located several miles apart. Only in extremely rich food sources will they nest in close proximity -- and although alert, is is not common for an osprey to attack another osprey unless they feel their nest or mate is being threatened. In this case, the bird made a close pass on the nest, and the male decided to escort the intruder away.
It was especially interesting to watch the house sparrows around the nest. These little birds were well aware that the osprey are fish eaters and had no interest in consuming them. But, the presence of the osprey certainly deterred other raptors, which might want the house sparrows for lunch! So these plucky birds were nesting underneath the osprey platform in the crevices. In fact, they would swoop up into the osprey nest and steal materials small enough to be incorporated into their own nests and carry them down under the platform. For the little birds, it was a win-win -- protection, and free nesting material! You can see 3 of them in this photo, and by my count, at least 6 were living under the osprey nest.
These birds have a rich and unique natural history, and were very charismatic to watch. I particularly enjoyed exploring the nesting items rejected by the female under the nest - and she continued to toss things out while I was under, almost bombing me with a piece of stump root that apparently did not fit the bill. The young, however, will remain deep within the nest almost until the age of fledging, when they will stand on the edge of the nest, largely ruining the beautiful structure constructed by their parents and often leaving the nest almost flat when they leave - at about 55 days of age. And the cycle starts all over again!
In theory.....my Instagram account is fixed. So we'll try another Instagram quiz. Any guesses on what species, and what behaviour we are witnessing in this photo? This occurred just last week in the marsh behind my home. If you'd like to know the answer - pop on over to my Instagram account to find out!