Northern Beaches Council is embarking on a novel approach to protect the nesting platforms of Osprey birds. Too often the birds choose temporary spots like private cranes at building sites – but these could soon be replaced with more bespoke options.
A 23-metre high metal pole with a circular aluminium mesh frame on top is currently being erected in Avalon, in a thicket between Hitchcock Park and Careel Creek mangroves.
Overlooking the Careel Bay Playing Fields, the pole, which resembles a golf tee, is actually an artificial nesting platform to provide an elevated home for the coastal-dwelling bird of prey.
Northern Beaches Council is overseeing this as a trial, which, if successful, is likely to see others installed along the Northern Beaches peninsula. The Avalon installation is expected to commence imminently and be completed by August 2024.
The best part? Birds on live webcam… the Avalon pilot program, a camera will be installed for live video feed of the nest.
The Avalon site is part of the Careel Bay Bushland Reserve, a wildlife protection area that Council describe as, “of high conservation significance due to the range of estuarine wetland vegetation communities it contains. They include mangroves, saltmarsh, seagrass and mudflats. The area is rich in species diversity and provides habitat for rare and threatened native animals which include migratory shorebirds”.
In explaining the incentive, Council declared:
“Ospreys have successfully taken up artificial nesting platforms at numerous other locations in northern NSW, South-east Queensland and South Australia. However, to date an artificial nesting platform designed for osprey has not been attempted within the Greater Sydney Region.
“We are proposing to take the lead and be the first Sydney Council to install artificial nesting habitat for osprey and monitor its success.”
When nesting, the female osprey lays two to three eggs, which she incubates for between five to six weeks. During this time, the male catches food and brings it to her at the nest. Once hatched, the juveniles remain supervised and fed in the nest until they learn to fly at around 9 weeks of age.
After maturation, around 22 per cent of osprey remain in the area or return with their partners in the breeding season. The rest disperse.
Ospreys are found around almost the entire circumference of mainland Australia, in close proximity to the sea and tidal waterways, but not southern Victoria or Tasmania.
Nesting sites
Ospreys, generally solitary birds except when they pair-up, breed and raise chicks, tend to be monogamous and remain with the same partner for life. They create large, often messy-looking nests, up to two metres wide, which consist of interlaced sticks and driftwood, which they line with turf and/or seaweed.
They renovate these structures, which weigh up to 135kg, on their return every year, and observers have reported nests up to 70 years old.
Ospreys tend to choose forks of trees, cliff faces or rocky outcrops on which to construct their nests, but will select human-made platforms such as navigation markers, radio transmission towers and abandoned jetties. Sometimes they build atop power poles or electricity pylons, which can create a significant risk of fire or electrocution that triggers power outages.
It is for this reason that artificial breeding platforms are necessary substitutes in suburban areas, which is a primary motivator for Northern Beaches Council.
As part of their background briefing on the Avalon location, Council said, “Provision is being made for an osprey nesting platform to replace a nest that was built on a private crane for a known breeding pair.
“Ospreys have been establishing large stick nests on temporary construction cranes and permanent infrastructure such as lighting poles at sports fields. We have received support to strategically identify opportunities for alternative habitat provision for ospreys on an as-needed basis.”
In January 2019, an 11.5 metres high artificial nesting platform was erected on the foreshore of Palm Beach, Queensland, to replace a nest that had been constructed by ospreys on a navigation beacon at the entrance to Currumbin Creek.
Although the beacon nest hadn’t been used for an indeterminate time, ospreys sometimes select different nests when breeding seasons come around and might return to a previously abandoned site. Hence the need by Gold Coast Waterways Authority to disassemble it and provide an artificial platform instead.
Osprey facts
This avian hunter, known by its Latin name, Pandion haliaetus, is of the order Accipitriformes (a distant cousin of hawks, eagles, vultures and kites – but not falcons). One of the larger raptor species, it differs from other birds of prey in several ways, including that its toes are of equal length.
It has a short tail but a wide wing span of 145-170cm, which features characteristic ‘fingers’ on the tips – four long and a shorter fifth.
They are typically dark brown in colouring on top of their wings and back, but white underneath, which effectively camouflages them against the bright sky to unsuspecting prey below. Although their top flight speed is around 50km/h, they can plummet up to 120km/h when dropping for a catch-and-kill.
Owners of dogs who walk around the Careel Bay Playing Fields, may now be reading this with trepidation, anxious that a stealthy, high-speed avian predator might suddenly descend and snatch poor Fifi for its meal. You needn’t be alarmed.
Ospreys are piscivorous – their diet consists of 99 per cent fish, which they prefer catching live (ospreys don’t consume carrion) Although they have been known to snatch snakes, lizards, rodents, frogs or other marine creatures. It is for this reason that they are also known as a sea hawk, river hawk or fish hawk.
In fact, the osprey is so well evolved to fishing that is has several specialised marine adaptations, unique from other raptors. These include:
* Closable nostrils to block water from entering their lungs during dives.
* Additional transparent eyelids, known as nictitating membranes, which close over their eyeballs like goggles and enable them to see underwater.
* Four clawed toes on each talon – three at the front and an opposable one at the rear, but the outer toe of the front three can swivel around, enabling them to grasp their prey with two toes in front and two behind. Called Zygodactyl, this phenomena is perfect for clutching struggling fish in their long claws. (Owls are the only other raptors with a reversible toe.)
* Reverse-facing scales on their talons with additional spicules (small spines) on the underside of their toes, which act as barbs and help secure their grip on their prey.
* Oily waterproofing on their plumage that prevents the feathers from getting waterlogged during submersion. This enables them to fully immerse themselves in the water to catch their prey, and removes the need to spread their wings to dry after dives, unlike cormorants.
Scientists report ospreys have a high success rate, around 70 per cent, when catching fish, which they sight from up to 40 metres above the water. On entering the water – feet first – ospreys also adjust their trajectory to take into account refraction in the water that can make a fish seem in a different position to where it actually is.
Declining habitat due to human activity
Ospreys are facing existential threats due to humans’ tendency to live by the sea, where they chop down trees and demolish other suitable nesting sites.
As Northern Beaches Council has acknowledged, “a key threat to the species is urban development, which has contributed to a significant loss of suitable nesting habitat (tall trees close to aquatic environments) across its range.”
On the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, ospreys, when last assessed (August 2021), were described as of Least Concern. This is a global assessment, because osprey numbers are believed to be increasing in the regions least at risk from urbanisation.
However, despite their extensive worldwide distribution – second only to the peregrine falcon – in some countries ospreys are in decline due to human encroachment on their coastal habitats, such as Britain, where there are only 260 recorded breeding pairs.
In Australia, the subspecies Pandion haliaetus cristatus – Australasian or eastern osprey, the smaller of the four subspecies – is listed as Vulnerable in NSW (May 2024) and Endangered in South Australia (January 2020).
And yet, according to the Australian Government-run Department of Climate Change, Energy, Environment and Water (DCCEEW), “there is no approved Conservation Advice for this species.” Furthermore, “there is no adopted or made Recovery Plan for this species.”
DCCEEW is co-funding the Avalon installation. Council declared, “The purpose of the [Avalon] project is to provide artificial nesting habitat for eastern ospreys (Pandion cristatus) which are listed as Vulnerable under the Biodiversity Conservation Act 2016 (BC Act).
“We would like to be leaders of habitat creation for threatened species on the Northern Beaches. This project, however, will be seen as a medium-long term trial and data will be collated to ascertain the success of the artificial nesting platform.”
Unlike the other three species, Australasian ospreys don’t migrate, and have a lifespan of seven to ten years (although in captivity that figure may double).
Osprey fact-file, Australian Geographic: https://www.australiangeographic.com.au/fact-file/fact-file-eastern-osprey-pandion-haliaetus-cristatus/
Council information on the program: https://yoursay.northernbeaches.nsw.gov.au/osprey-nesting-platform-avalon
