This may seem like a dumb question, but I wondered if it was possible for different species of birds to produce viable offspring. I started pondering it because I saw a cardinal coming on to a robin this morning.
Horses and donkeys produce mules, lions and tigers produce ligers or tigons, different breeds of dogs can make all variety of mutts. So can birds do this as well? I’m not talking something crazy like say, a goose and a hummingbird. I mean more along the lines of two different types of songbirds.
Hybridization happens all the time in songbirds. One of the best examples of this is the Baltimore Oriole and Bullock’s Oriole, which hybridize so extensively that for a while they were thought to be the same species (called the “Northern Oriole.”)
According to the Biological Species Concept, species are defined as those populations that do not regularly produce fertile hybrids in nature in places where they co-occur (or, for those that do not co-occur, have a similar level of difference as known related species).
Some species of ducks are fully interfertile in captivity, but rarely produce hybrids in nature due to differences in courtship and other behaviors. There are many other closely related species that may produce hybrids on occasion where their ranges overlap, or under special conditions.
The more distantly related the species, the less likely that hybridization will be possible. However, sometimes quite distantly related species may be able to hybridize. Hybridization within the same genus is fairly common; between genera in the same family much rarer; and between families nearly non-existent.
Cardinals and a Robins belong to two different families within the songbirds, and are sufficiently distantly related that hybridization would probably be impossible.
This change was largely due to changes in the interpretation of the Biological Species Concept over the past 50 years. Formerly, if there was any evidence of hybridization at all two forms would be lumped as the same species. Nowadays, the standard has shifted, and as long as hybridization is confined to a narrow zone or is rare the two forms will be split as different species. In the 1960s or 1970s the two former species were lumped because they hybridize occasionally in a narrow zone. More recently they were re-split because it was decided the extent of hybridization was insufficient to qualify them as the same species.
Aren’t robins insectivores, while cardinals are seed-eaters? That right there would seem like a big enough difference to me. Any hybrid of the two would likely have a horribly mangled beak that couldn’t eat anything. So it sounds like you just have a very perverted cardinal, there.
Pretty interesting stuff. Thanks for the in-depth explanation, Colibri, that explains a lot.
I’m not sure the cardinal was so much perverted as he was desperate. I’ve seen lots of males around here in the past few months but only a handful of females. He probably saw the splash of red on the robin’s breast and figured it would be better than nothing. At any rate, he kept sidling up and trying to mount her. She looked more confused than anything.
Funny you mention ducks. There are mallards and Muscovy ducks here at my office building, living in the ponds around the building and interbreeding like mad. My favorites so far have been the “mallards” with brown or copper head feathers (instead of green) and the “Muscovy ducks” with brilliant green feathers on their wings.