Letter-winged Kite on the Brink?

Letter-winged Kite - Pic by Peter McDonald

One of Australia's iconic raptors may be seriously at risk of extinction. The fate of the Letter-winged Kite appears to have escaped the notice of the authorities and, for the most part, the birding community. It is likely that feral cats are the cause of a crash in populations of the world's only nocturnal raptor, and that protecting dingoes may be a key part of the solution to save the species.

I became concerned about the kites during an influx of predominantly inland bird species to coastal areas in 2012-2014. These movements occur from time to time following periods of heavy rainfall inland, when birds breed prolifically. When floodwaters subside and ephemeral wetlands dry up, many birds move to coastal areas. Letter-winged Kites are often among the mix; during one such influx for instance, I found several kites on the beach on North Stradbroke Island (see here) in 1977.  In 2012-214, however, there were no reports of Letter-winged Kite from coastal eastern Australia although several other predominantly inland species (such as Black Kite, Black-tailed Native-hen and Australian Painted-Snipe) were turning up in regions such as south-east Queensland, where they are normally absent.

Something appeared to be amiss. Meanwhile, birders travelling the inland were reporting seeing fewer and fewer kites as the years progress in areas where they were once reliable and even quite common at times. The plight of the Letter-winged Kite is highlighted in an article by Sean Dooley in the newly published December 2015 edition of Australian Birdlife; at the time of writing I've not had the opportunity to see the article, but it is encouraging that attention is now being drawn to the matter.

The rainfall events referred to above are usually associated with explosions of populations of the Long-haired Rat (Rattus villosissimus) and other native rodents upon which the kites feed. Letter-winged Kites congregate and nest during these explosions; when rodent numbers subside, kite numbers also decline and the birds disperse. 

Feral cat in a Letter-winged Kite nesting tree - pic by Lindsay Cupper

Chris Pavey, an arid zone ecologist with the CSIRO, reports the results of surveys on Andado Station in the south-east of the Northern Territory following two such rodent explosion events in 2001-2002 and again in 2011-2012. In 2001-2002, a maximum count of 121 Letter-winged Kites was recorded. In 2011-2012, the maximum count of kites was just 9. Although local factors may have influenced this discrepancy, it is a quite a dramatic demonstration of what appears to be going on out there.

Feral cats have been around for many decades but anecdotal evidence suggests that populations are increasing in northern and central Australia. The kites are likely to be impacted in two ways. Adult kites and chicks are known to be killed by cats during nesting events, with entire colonies having been eliminated by feline predation.

As well, cats compete with kites for rodent prey. A study by Chris Pavey and colleagues Stephen  Eldridge and Mike Heywood looked at competition between kites and three introduced mammalian predators - dingoes, foxes and cats - over 3.5 years in the early-2000s. They concluded there was considerable potential for food-based competition between the kite and mammalian predators, particularly foxes and cats. While Letter-winged Kites had a very narrow dietary niche (native rodents), mammalian predators could exploit other prey in lean times. The scientists concluded that the mammalian predators captured 11 times as many rodents during the study period as the Letter-winged Kites.

Feral cats in Letter-winged Kite nest. Pic by Jack Pettigrew

In 1992, an unusually large concentration of feral cats at Davenport Downs Station (now Astrebla National Park) in south-west Queensland attracted national media attention. At one point, 85 cats were counted at rest in 73 coolabah trees. Many were lying in nests that had been used by Letter-winged Kites just weeks earlier. What was not widely reported at the time, however, was that similar concentrations were not being noted in areas of similar habitat elsewhere in the region.

Dingo at Night Parrot site. Pic by Steve Murphy

University of Queensland scientist Jack Pettigrew, who is something of an authority on the species, concluded that the explosion in cat numbers at the site was related to the recent shooting at the time of more than 50 dingoes in the area. Jack is not alone in suggesting that protecting dingoes may be crucial to controlling feral cat numbers and the long-term survival of Letter-winged Kites and other endangered species. Research scientist Steve Murphy has suggested that dingoes may be playing an important role in controlling cat numbers in the area in south-west Queensland where Night Parrots were discovered by John Young in 2013 (see here for more).

Letter-winged Kite. Pic by Lindsay Cupper