Not many birds are provided special poles with platforms upon which to make their outrageously large nests. But the Eastern Osprey, at least in NSW, with their preference for sites overlooking prime coastal fishing spots, are sometimes granted that special concession.
Pandion cristatus is a medium sized ‘fishing eagle’, listed in NSW as Vulnerable under the Threatened Species Conservation Act (1995). They typically nest in large (or ‘emergent’) trees, or older dead trees that provide good vision and access to coastal waterways, where they can fly out to find fish and return to feed. These habitat requirements of course are increasingly difficult to satisfy due to ongoing competition from human activities such as speed boating, farming, tourism and urban development in coastal and riverine areas.
Consequently, when a pair of breeding birds begins developing a nest at the top of power poles, bridges, or other human infrastructure, a number of government agencies and utilities in the state of NSW have been known to provide specially constructed Osprey poles nearby for them instead (Byron Bird Buddies community group also built their own structure).
The Osprey is actually found more or less worldwide (except for Antarctica), with a number of sub-species known. In Australia, they are mostly found in the more northern climates, being generally absent from Victoria and Tasmania.
The Yuraygir National Park provides significant habitat for this species. 65 km of coast, much of which is Marine Park as well, offers excellent fishing opportunity, with large stretches of undeveloped foreshore offering scope for seaside nests. The Sandon, Wooli and Red Rock Rivers and a range of hind dune lake systems also offer superb estuarine, riverine and lagoon areas supporting this species.
So it was not so surprising perhaps, but certainly exciting to realise that just across from one of the highest points in Minnie Water, in the top of a Norfolk Pine, a new Osprey nest was created over Winter and Spring this year.
Ospreys are a marine raptor, and there several other species that overlap with some of the habitat and habits of this bird, including sea eagles and several species of kite. So how can you tell them apart?
Sea eagles are much larger than Ospreys, and have that very distinct fully white head and belly, with V-shaped white underwing that is then trailed by a dark rear underwing. Sea-eagles soar with wings bent upwardly, compared with Ospreys which tend to have more bowed and more constantly active wing movements.
Ospreys tend to be slightly larger than the Brahminy and Whistling kites which are also commonly seen on the Yuraygir coast. They have dark brown upper body colours, with light undersides, and a distinct black band through from the eye toward the back of their white head. (Kites tend to have very pronounced dark coloured fingertip like wing feathers, with the Brahminy an obvious rusty red and white colouration, and the whistling kite a mix of sandy and darker colours with no white).
If you are lucky enough to see its nest, you will be able to confirm it is that of an Osprey generally, as they make quite distinct, large heaped nests using sticks, seaweed and other materials. Because they are often re-used for many years, these nests can grow to as large as 2 x 2 metres.
Ospreys’ beaks are strongly hooked for the tearing of fish flesh and they have very powerful legs used in the capture of their sub-surface prey. They almost entirely feed on medium sized fish which they catch in their talons, which have barb like backward facing scales. They will fly out over the water and dive suddenly for prey, and will lift off from the water and return to a perch before ripping it apart to eat.
Some of their other adaptations are closable nostrils to prevent water ingress during dives, and very dense, oily plumage to prevent water-logging of their feathers.
Australasian ospreys do not migrate, unlike others elsewhere on the globe, and typically pair and mate for life from the age of 3-4 years. Females tend to be slightly larger, but otherwise they are similar in appearance.
Breeding season in NSW is between July and September, and the female generally lays 2-3 eggs and incubates them for up to 40 days while the male finds food, occasionally swapping roles. The female also typically takes on most of the nestling management, with both parents actively involved in food gathering later in the cycle. Fledging occurs at around 9 weeks and the young will return to the nest to feed as well for up to two months.
They maintain a territorial area throughout the year, including defence against other raptors and potential egg and hatchling predators. The size of their territorial range is not known, but is likely to be up to about 3 km from their nest site.
The Osprey is a top order predator of the sea, and a relatively rare bird in NSW. Humans have competed with it for habitat in the areas it has evolved to exploit and of course, they have heavily exploited the foods upon which the Osprey also depends.
Although it is not nationally listed as threatened, it is ‘vulnerable’ in NSW under current state legislation. This affords it certain protections in terms of planning considerations, but Yuraygir National Park and Solitary Islands Marine Park remain a significant stronghold for this species.
It is important we remain aware of the species above us on the coast and that we understand their role in the broader ecology. National Parks are always keen to hear from the public when they spot a threatened species so they can map their location and maintain up to date records to better help protect them.
Here on the Yuraygir coast, we are so lucky to have these birds literally living and breeding in our backyards.
We wish to thank Daniel O’Sullivan for his excellent series of photos of this Osprey family this Spring. More of his photography can be found on his Facebook page.