Some readers may be interested in these further ideas on this issue. He is OK for me to pass this on. He also sent me a pdf of the publication. I think it important
to note (for those interested) that the experiments referred to do NOT apply to cuckoos. We in Aus, would think first of cuckoos in that context, which is why I thought it just does not sound right.
Philip
From: Philip Veerman [
Sent: Tuesday, 1 March 2016 10:21 PM To: 'Matthew Louder' Subject: RE: How Does a Cowbird Learn To Be a Cowbird? | Audubon
Hello Matthew,
Thanks for your quick reply. I suspect that cowbirds and the redhead duck are evolutionary fairly recent situations. Cuckoos are likely to be much older situations,
so although they are still evolving strategies (as are their hosts) the potential imprinting problem is likely to have been worked through by now, such that it is not even close to an issue for cuckoos. I hope you don’t mind if I forward your comments onto
others, as they clarify the original summary.
Philip
From: Matthew Louder [
Sent: Tuesday, 1 March 2016 9:53 PM To: Philip Veerman
Subject: Re: How Does a Cowbird Learn To Be a Cowbird? | Audubon
Hello,
Thank you for taking an interest in this article.
“In laboratory experiments, cowbirds and other brood parasites that spend too much
time with their foster families end up learning their host species’ songs, picking up their behaviours, and attempting to mate with them.” I wonder if that is a misquote that
this is something they need to avoid. I am sceptical of that this happens at all, at least in cuckoos, let alone what is implied here as occurring regularly. I wonder what other brood
parasites species that applies to.
There have been two experiments, one with parasitic cowbirds and the other with parasitic Redheads (a North American parasitic duck) that demonstrate that brood parasites can imprint on their host if they remain in contact for an extended
period of time. In each case, the birds attempted to mate with their hosts. However, I was pointing out these studies not to say this happens regularly, or at all, in nature. Rather, I was attempting to point out that cowbirds and other brood parasites can
imprint on their host, but in nature, they leave their host before this would happen. To date, no one has attempted to see if cuckoos will imprint on their host if they remain in contact for too long, but I would expect that it might happen too. Indigobirds
and whydahs are the most likely to imprint on their host, as they adopt some of the host song into their own repertoire, but they too separate from their hosts in nature and no one has attempted the imprinting experiment.
References to the experiments I quoted:
Freeberg, T. M., King, A. P., & West, M. J. (1995). Social malleability in cowbirds (Molothrus ater artemisiae): Species and mate recognition
in the first 2 years of life. Journal of Comparative Psychology, 109(4),
357.
Sorenson, M. D., Hauber, M. E., & Derrickson, S. R. (2010). Sexual imprinting misguides species recognition in a facultative interspecific
brood parasite. Proceedings of the Royal Society of London B: Biological Sciences, 277(1697),
3079-3085.
I also wonder how someone would know that by the time they’re about a month old, they
know to mate with their own species. What birds are sexually mature at one month old? Are these cowbirds mature that quickly?
The cowbirds do not sexually mature at one month, and I agree that this is confusing how its worded. I believe the author was trying to say how cowbirds leave their host at one-month-old and learn their own species, i.e. learn who to mate
with. Although they are learning who to mate with at one month, they do not act on this until the following year.
Hopefully this helps somewhat. Thank again,
Matthew McKim Louder
Postdoctoral Fellow
Department of Biology
East Carolina University
Department of Psychology
Hunter College, City University of New York
mimlouder.weebly.com
On Feb 29, 2016, at 11:38 PM, Philip Veerman <> wrote:
Hello, this has just come through and I thought I would comment or ask...... I know little about cowbirds, as they don’t occur in Australia but we have many
species of parasitic cuckoos (and one non parasitic species of cuckoo).
Well that is a strange strategy. But what I find strangest is the starting statement that. “In
laboratory experiments, cowbirds and other brood parasites that spend too much time with their foster families end up learning their host species’ songs, picking up their behaviours, and attempting to mate with them.”
I wonder if that is a misquote that this is something they need to avoid. I am sceptical of that this happens at all, at least in cuckoos, let alone what is implied here as occurring regularly. I wonder what other
brood parasites species that applies to.
I could sort of go along with this for the parasitic whydahs and their weaver finch hosts where there is some song transference to parasite chicks. But I think even that is a stretch. I also wonder how someone would know that by
the time they’re about a month old, they know to mate with their own species. What
birds are sexually mature at one month old? Are these cowbirds mature that quickly?
How Does a Cowbird Learn To Be a Cowbird?
When a Brown-headed Cowbird hatches from its egg, an identity crisis seems inevitable. Cowbirds are brood parasites, meaning that rather than raise their young themselves,
they ditch their eggs in other species’ nests and allow these forced foster parents to do the tough work of chick-rearing. Baby cowbirds grow up with families that neither look nor act anything like them—sometimes in habitats in which cowbirds typically don’t
even live.
“Cowbirds have to figure out who they are without their biological parents,” ecologist Matthew
Louder says. The shocking thing is that somehow, most of them do—and in a
recent study, Louder shows how. Like human teenagers, young cowbirds sneak out at night—though unlike human teenagers, these chicks’ evening rendezvous seem to be with members of their own family.
In laboratory experiments, cowbirds and other brood parasites that spend too much time with their foster families end up learning their host species’ songs, picking up their
behaviors, and attempting to mate with them. In the wild, though, they’re somehow able to resist this—by the time they’re about a month old, they’ve learned to act like cowbirds, and they know to mate with their own species. The more Louder looked into the
question of how they do it, though, the more he realized we really don’t know. “It’s kind of bothered people for a long time,” he says.
Louder recently published a study that showed that
cowbird moms don’t totally abandon their young after laying their eggs, but keep tabs on them and even use the failure or success of different nests to inform their decisions about where to lay future broods. His colleague Mark
Hauber suggested that these watchful mother birds may also be keeping their chicks from getting too close to their hosts. Maybe, the team thought, adult cowbirds have some contact with their offspring,
which is how the chicks learn the ways of the cowbird.
To test that idea, the researchers attached
radio transmitters to adult cowbirds and their young. The data revealed that the juveniles didn’t follow older birds away from the nests and rarely ventured to their mothers’ homes. Instead, they go on
nighttime rendezvous.
“They seemed to, just one night out of the blue when they were about 20-25 days old, say ‘Oh man, I need to go somewhere,’” Louder says. “It’s almost like zugunruhe,
or migratory restlessness.”
The data showed that
young cowbirds leave the host nests shortly after sundown and roost overnight in the fields where the species typically lives before returning to their foster families the next day.
“When I saw them do it, I was just shocked. You’re gonna leave in the middle of the night to go somewhere you’ve never been?” Louder says. “To me, it just seems that would
be the most dangerous time to do this, and that’s what led us to believe that it’s extremely important.”
The team thinks these night flights—which may be spurred by an innate preference for roosting in fields—give the cowbirds some independence from their foster parents and
keeps them from becoming something they’re not. Since adult cowbirds roost together at night in the same fields, the young birds’ excursions could also give them the opportunity to mingle with their own species and learn the right behaviors.
Louder thinks his results help show that even parasites have to work hard to survive. “There's this weird animosity towards cowbirds among the public,” he says, but in his
mind, it’s not deserved. Not only do the adults have to trick the hosts, sneak their eggs in, and keep an eye on different nests, but the chicks have to put some effort in just to learn to sing, forage and act like cowbirds.
“These guys are really cool. They have these crazy behaviors and what they're doing is really complex,” he says. “If this was easy, everybody would do it.”
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