dv said:
So Arts informs me there are no crows in Perth, only ravens.
So what the heck is a crow, and what is a raven?
The genus Corvus contains about 47 species. I say “about” because different sources regard certain members as subspecies of other species.
Of these, one is called the rook, two are called jackdaws. “About” 11 are called ravens, and the rest are crows.
There is not a scientific or objective distinction between the categories, and the groups are not monophyletic: that is to say, the set of “ravens” is not defined by a common ancestor, and nor is the set of crows. For various historical reasons some corvids are called ravens, and others are called crows. The ravens are mainly fairly large corvids but there are exceptions.
The members of Corvus found in Australia are:
Corvus coronoides, Australian raven, found throughout southern Western Australia, and other mainland states.
Corvus bennetti, Little crow, found throughout southern Western Australia, South Australia, NT and arid parts of Qld and NSW.
Corvus mellori, Little raven, found in Victoria, NSW, South Australia.
Corvus orru, Torresian crow, AKA Australian crow, found in Qld, NT, northern WA, northern NSW, northern SA, PNG and Indonesia
Corvus tasmanicus, Forest raven AKA Tasmanian raven, found in Tasmania, Victoria, NSW, SA
Both the Australian raven and the Little crow are found in Perth: the Australian raven is about 15% larger and is apparently much more common in Perth, as the Little crow prefers the drier coastal areas to the north. Of the Little crow, Wikipedia says, “Its food is mainly taken from the ground and includes insects, cereals and other seeds. It is less of a scavenger or carrion feeder than the other Australian species. It usually nests in small, loose colonies, building stick nests lined with mud (the only Australian species to do this).”
http://www.birdlife.org/datazone/speciesfactsheet.php?id=5787
http://www.birdlife.org/datazone/species/factsheet/22706027
http://www.birdlife.org/datazone/species/factsheet/22706033
We have a very similar situation in Melbourne. We have the Little Raven (Corvus mellori) and the Australian Raven (Corvus coronoides). Differences between the two are supposed to be that:
The Little Raven is slightly smaller.
The Little Raven is a social bird whereas the Australian Raven defends its territory except where food is plentiful.
The Little Raven nests lower down on trees, the Australian Raven higher.
The Little Raven has an extra ka ka ka call.
I note also on some old maps a weird curved line separating the domains of the Torresian Crow (north) from the Australian Raven (south). In the oldest of these the domains abut but don’t overlap at all across the entire continent form east to west, in more recent maps the domains do overlap in Queensland and don’t overlap in Western Australia.
Differences between the Australian Raven and the Torresian Crow are supposed to include that:
The Australian raven has a white under-feather on its throat (not visible from a distance)
The Torresian crow has an extra drawn-out Aaaaaaaagh call.
Despite watching these birds in Sydney, Brisbane and Melbourne for over 30 years I’ve never been able to tell the difference between the species. For instance in 20 years of crow-watching in Melbourne I’ve never seen any bird that I can definitively say “that is an Australian Raven”. We have two pet ravens at the moment, siblings, that free to come and go but we’ve fed them every day since they were nestlings.
About 25 years ago, I became curious about where the thin line separating the domains of the Australian Raven and Torresian Crow came from. I tracked it down to a CSIRO article sponsored by Australian sheep farmers who wanted to know which species of Australian Corvus attacked live lambs. The article concluded that there was no conclusive evidence that any species of Australian Corvus attacked live lambs. The original article is from 1970. On the web it’s $25 to view. I probably have a photocopy somewhere but over that time it’s sure to be as close to lost as anything is. I’ve been waiting patiently since that time for someone to do genetic comparisons on Australian Corvus species, but nobody has. By the way, Google just popped up this quote “The corvid family has its origin on the Australian continent”.
The Genus Corvus (Aves: Corvidae) in Australia
I Rowley
CSIRO Wildlife Research 15(1) 27 – 71
Published: 1970
Abstract
The taxonomy of the genus Corvus in Australia is reviewed on the basis of field studies and a large collection of new material from most parts of the continent. Five species are recognized, four of which are endemic to Australia (C. coronoides, C. mellori, C. tasmanicus, and C. bennetti) while the fifth, C. orru, is shared with New Guinea and islands to the north. On the basis of this material no races of C. coronoides, C. bennetti, or C. mellori are recognized and only one race of C. orru (C. o. cecilae) is found to occur in Australia. Two races are suggested for C. tasmanicus, C. t. tasmanicus and C. t. boreus; the latter has been undescribed hitherto. A key to the separation of the five species is presented; characters likely to assist field identification are described; and the details of species diagnosis, measurements, and distribution are given. The possible evolutionary pathway of these forms is discussed.
