Book Length Project Group Member, Margaret O'Brien's project on ospreys

 

Old Ma Osprey

Margaret O'Brien is writing a non-fiction natural history book focussing on one breeding season in the lives of a family of ospreys in Perth, Western Australia. Based on her own observations, the text is complemented throughout with the author's photographs of an osprey family in crisis.

Author and photographer Margaret O'Brien

Margaret sent me some pictures of the next generation of ospreys in the same nest. These ones won't appear in the book. Please note that for all photographs pertaining to this post the copyright is held by Margaret O'Brien.

Female osprey coming in for a landing. Adult female ospreys typically have a prominent bib of darker feathers across the chest, whereas the males have sparse markings or a pure white chest.



Mother osprey with 5 week old chick. This chick was the single survivor of three hatchlings from the 2010 nesting season. It fledged at 9 weeks. Judging by its large size, it was presumed to be female, males being noticeably smaller.

 

Male (at rear) and female osprey at the nest at the beginning of the 2009 nesting season. They are peering at an egg or eggs (unseen). Both birds incubate the eggs, though it is predominantly the female's role and the female always incubates overnight.

Close shot of the mated pair of ospreys on their nest at the beginning of the 2009 season. Ospreys mate for life, with sexual maturity occurring at 3 years of age. The female (front) is the larger of the two.



A family of Willie Wagtails have their own nest in the scrub at the base of the osprey's nest tree. They fiercely and persistently try to chase the ospreys out of their territory. The ospreys take the attacks as a minor irritation and never respond with aggression. Here, the Willie Wagtail zeroes in on the female osprey like a heat-seeking missile.

 

Adult female on one of the branches leading from the nest being pestered by a territorial Willie Wagtail.

Recently fledged osprey about to cop a Willie Wagtail in the neck

Female osprey with approximately one week old chick. Until they are 10 days old, ospreys chicks are unable to regulate their own body temperature and are totally reliant on their parents for thermoregulation.

Female osprey and chick on the nest. The iris of adult ospreys are pale lemon to yellow, whereas those of the chicks are more orange.

The male brings a live fish to his mate on the nest. Ospreys feed exclusively on live fish, which they catch by diving feet first and up to a metre into shallow water. It's a horrible death for the fish which the osprey anchors with its powerful talons and eats the still very much alive and struggling fish from the lips backwards. It's always very confronting to watch and more than at any other time, I need to remind myself of the timelessness of what I'm observing and that ospreys having been doing this for tens of thousands of years.

Juvenile osprey with partially eaten fish. This young bird hadn't long fledged; in this shot the fish was provisioned by its father. There is no evidence that fledglings are taught to fish by their parents. From my observations, the young birds start to gain some proficiency several weeks after fledging, though their first catches are invariably blowfish.

The 2011 nesting season was hugely successful, with three chicks fledged. The two on the right are presumed females (because of their larger size), with a presumed male on the left. Males are smaller and usually fledge before their female siblings, which is what happened with this trio. Expert examination and DNA testing is the only sure-fire way of determining gender of young birds. The sex of adults is more easily determined, the female being larger, with a more prominent band of darker feather across the chest.



I was on the river in my kayak when I saw this osprey patrolling for fish. It's talons opening and closing continuously, it made fine adjustments with its wings, rising and falling in the air and never taking its eyes off its prey before eventually plunging feet first into the water.

It isn’t only Willie wagtails that aren’t fond of ospreys. An Australian Raven and its mate (out of the picture) eventually succeed in driving this one out of the tree.

Osprey emerging from a dive. A fishing osprey is one of Nature's most spectacular sights, the water exploding for several feet around the bird, in part due to the displaced water, but in instances where it plunges into a school of fish it causes the school to scatter in a chaotic frenzy.

With its prey in its talons, the osprey climbs about 20' into the air where it shakes itself vigorously to shed its feathers of water. It then realigns the fish to face forward to reduce aerodynamic drag before flying to a favourite perch to eat it or to deliver it to the nest.