BirdLife International report states that threats to birds are of ‘humanity’s making’. BirdLife International is the largest international partnership for nature conservation. They are a go-to organisation to understand the status of birds on the planet in respect of their conservation and decline in numbers.
As one of 15 different non-native species, the contribution of cats to negatively impacting bird populations represents about one fifth of the total damage done by non-native animal species based on their data. This puts things in perspective.
At the head of their website, they state unequivocally that: “People are destroying and consuming nature at a devastating rate. Birds are our early warning system.”
They have a detailed study on their website which looks at a crisis affecting the world’s birds and why bird numbers are declining. The decline is because of humankind’s behaviour. That’s what they say.
They are not directly blaming the domestic, stray or feral cat. Let’s be clear about that. Yes, the domestic and feral cat is an invasive species in some places and they do impact bird numbers negatively. We all know that. This organisation states the obvious – but it needs to be stated – in that people brought the cats to those places. Invasive species are the product of human behaviour. We know that too but it also needs to be stated.
Historically, the domestic and feral cat has been blamed as if these animal are directly responsible. Australia is very fond of doing this. But they are myopic about it. It all boils down to human behaviour at the end of the day.
Specifically, BirdLife International state that “Agricultural expansion, logging, overexploitation, urbanisation, pollution, disturbance and the effects of invasive alien species are all driving bird declines and diminishing the natural world.”
There is a hint there of the involvement of feral cats. I can see that. But the thrust of the argument is that this is about people. And of course, they agree that human-induced climate change may be the most damaging factor in the survivability of birds.
Most species of bird are impacted by multiple threats such as land clearance for agriculture being preceded by deforestation or the drainage of wetlands.
And in some areas, global warming exacerbates the threat posed by avian malaria. It does this by extending the area of suitable habitat for malaria-transmitting mosquitoes.
Direct human behavior is responsible for most of the threats to birds. That’s what they say. And foremost among these human threats is agricultural expansion and intensification. This impacts 1,091 globally threatened birds (74%). Logging affects 734 species (50%). They state that invasive alien species threaten 578 (39%) species. Hunting and trapping negatively impacts 517 species (35%).
They state that agricultural practices are unsustainable. Although there have been no scientifically confirmed cases of domestic and feral cats causing the extinction of birds on the mainland, there have been examples of this occurring on islands.
This is referred to in the BirdLife International report. But rightly they emphasise the fact that “humans have been transporting animals and plants around the world for thousands of years”. The point here is that if feral cats cause extinction of a bird species on an island, the underlying reason is human behaviour.
And when we refer to invasive species, we have to refer to over 1,500 species which have become established outside their natural geographical ranges because of human importation of the species. They state that “rats and cats have had by far the greatest effect, threatening the survival of hundreds of bird species worldwide”. However, many bird species are affected by multiple impacts from a range of non-native species.
A good example is the Galapagos Petrel. They say that numbers of this bird species have declined rapidly since the early 1980s because of a variety of threats including “predation by introduced rats, cats and dogs, and the destruction of breeding habitat by introduced goats and cattle”. That provides a much more rounded picture as to how introduced species i.e. non-native species, can threaten the survivability of a bird species.
They also state that an analysis of the number of globally threatened bird species affected by different types of invasive alien species found that rats and mice affected 250 bird species while domestic cats affected 202 species. The dog negatively impacted 79 bird species and the domestic pig 66 species.
In their chart which I have reproduced on this page, they list the invasive species which have negatively impacted bird species. There is a total of 941 bird species impacted by 15 different species of non-native animal including domestic and feral cats. Cats impacted 202 bird species as mentioned. The contribution of domestic and feral cats to negatively impacting bird population numbers out of all the non-native species is 21.4%. That’s about one fifth.
To clarify, if you take all the non-native species on the planet and measure the damage that they do to birds, cats’ contribution is one fifth of the total. This I believe is in stark contrast to the impression that we get from ornithologists and the Australian government that feral cats are the primary culprit and therefore they have to be exterminated. This simply isn’t true.