The Osprey (Pandion haliaetus) is a widespread and common migratory bird of prey. They can be seen throughout the year in some parts of California and Florida, although they are summer visitors to the rest of their wide breeding range which extends to Alaska and includes most of Canada and large parts of the eastern and western contiguous United States.
These cosmopolitan birds can also be seen on every other continent except Antarctica and are breeding visitors to the United Kingdom and other parts of Europe.
Male and female Ospreys are very difficult to tell apart out in the field. The most visible difference between males and females is the breast-band, which is usually more prominent in females. A more reliable, but less visible, physical difference between male and female Ospreys is their weight.
Females are typically 15 to 20 percent heavier on average. The female is also larger in other measurements, although there is too much overlap for those metrics to be much use.
The difficulty of telling between male and female Ospreys can be a welcome challenge for keen bird watchers since careful observation of their habits can be very useful for making a positive identification.
Differences in behavior at their summer breeding grounds are often much easier to observe than the minor physical differences between the sexes.
Visiting an Osprey nest site is a wonderful way to watch these birds interact and observe the various differences in their appearance and behaviors.
Read on to learn how female Ospreys differ from males and how you can identify the sexes while birdwatching.
Male (left) and female (right) - Ospreys look extremely similar, with size being one of the best ways to differentiate
Male and female Ospreys look very similar. The difference in the amount of dark plumage in the breast-band is the most obvious visual marker, although comparing the size of the birds in a pair can also be effective. Male and female Ospreys are probably most reliably told apart by watching the breeding behavior of a nesting pair.
Read on to learn more about the visual differences between male and female Ospreys.
Male Ospreys are large hawks with long, narrow wings. They appear all dark above and white below. There is a bold, dark brown stripe that extends from the yellow eye to the nape while the throat and back of the head are white.
There is a variable amount of dark streaking on the crown and usually little dark patterning around the neck. Ospreys have longer feathers on the nape and back of the head that can be lifted somewhat.
Male Osprey in flight - lacking the upper breast band coloring
Female Ospreys look like males but tend to have more dark-colored feathers across the upper breast (breast-band).
Female Ospreys, like males, are mostly dark brown above and white below. The bill is blackish and the eye is yellow.
Close up of a perched female Osprey - see the dark upper breast band
There aren’t any well-known names that apply specifically to female Ospreys, although most female hawks can be called hens.
Female Ospreys are significantly larger than males. The difference is most noticeable when comparing their weights. Male Ospreys typically weigh between 42 and 53 ounces (1200 - 1500 g), while most females weigh between 56 and 70 oz (1600 - 2000 g). The difference is typically between 15 and 20%.
Female Ospreys also have longer wings, tails, claws, and bills, although there is more overlap in these measurements.
Female (left) and male (right) nesting pair of Osprey
Looking out for behavioral differences is a great way of identifying male and female Ospreys. These differences are most obvious when the birds are breeding and nesting.
Continue reading to learn about the easiest observable differences in male and female Osprey behavior.
During the breeding season, the male Osprey usually sleeps near the nest but not on it. He also uses this perch for feeding and relaxing during the day. The female moves off the nest and begins to roost nearby when the chicks are nearly at fledging age.
The male does practically all of the hunting while the pair are nesting. He feeds the female even before the eggs are laid and incubation begins. The time he spends hunting increases significantly once the eggs have hatched.
During nesting, males practically do all of the hunting
The female Osprey begs for food from the male by leaning forward to hold her body parallel with the nest and by slightly raising her crest feathers. She may beg when the male has arrived back at the nest with food, or encourage him to go out and hunt.
Male Ospreys put on a dramatic display while courting a female and during the early stages of nesting. This display is commonly known as sky-dancing and consists of a high, undulating flight with a lot of calling. The male often performs the sky dance when bringing food or materials back to the nest.
Male Ospreys are protective over their partners, particularly in the time leading up to the eggs being laid. He will follow his partner and keep any rival males from approaching her or the nest site. This appears to be quite effective since mating with rival males is rare.
A male osprey making a final approach towards the back of a female bird on the nest for the purpose of mating
Both male and female Ospreys call frequently. The sounds they produce are similar, but observing the behavior of calling Ospreys can be a reliable way to tell males from females.
Both males and females produce similar calls, but often for different reasons. Both sexes produce an alarm call when a predator or human approaches the nest, although the female produces this call most often.
Females also have a begging call that can be heard throughout the nesting period. Males are more likely to produce an excited screaming call, often while displaying.
Adult Osprey on the nest with two chicks
Ospreys are long-lived birds. Individuals of both sexes have lived to be over 25 years old.
Ospreys are usually monogamous and pairs will return to the same nest site year after year. It is usually the male who is first to arrive, however. Both partners work together to ensure the survival of their chicks, although each parent has different responsibilities.
Continue reading to learn more about the roles of nesting Ospreys and how you can use their behavior to identify males and females.
The male Osprey is usually responsible for selecting the nest site, although the female is also often also involved. Both partners participate in nest building, and each has different roles. The male brings in the majority of the nesting material while the female places and arranges the sticks.
Males usually bring in the majority of the nesting materials, whilst the female arranges it
Female Ospreys spend most (up to 95%) of their time on or near the nest. Males do assist in incubating the eggs, however, and are often responsible for as much as 30% of incubating during the day. In some cases, males even do more day incubating than females.
Once the eggs have hatched, the female does almost all of the brooding. Once the chicks are too large to brood, she will continue to shade them with her open wings on hot, sunny days.
Males are responsible for feeding the female and the chicks once they have hatched. The amount of time he must spend hunting increases dramatically when he has as many as four or five hungry mouths to feed.
The female usually moves a short distance from the nest to feed. The male will take over the duty of incubating the eggs while she feeds. Once the eggs have hatched, the female feeds the chicks with the food that the male brings in.
Male Osprey brining a fish back to feed the female and chicks
It is possible for female Ospreys to raise young alone, although their chances of success are very low. There is a record of a female Osprey successfully raising a single chick to fledge all on her own.
The male Osprey is responsible for feeding the female while she incubates the eggs and then feeding the chicks when they have hatched.
Without the help of a male, most eggs do not hatch because the female needs to spend time foraging away from the nest. This leaves the eggs vulnerable to predators and large temperature variations.
Whilst it's possible for female Ospreys to raise young alone, the odds are usually very low
Female Ospreys call for various reasons. Their calls are louder and deeper than those of males, although this can be difficult to compare unless both sexes are calling.
The following calls can often be heard while she is at the nest:
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