Thanks. Yes it's curious and hard-to-believe and I think that's why I remember 
so clearly reading about this in the Lab of O's Living Bird member's magazine, 
but as I said, can't find that article online--perhaps it is only in their 
printed version which I must have read 2017 or later. AllAboutBird account is 
much earlier, 2009, and does not bring up what must be some NEW research (

Regardless, just now a friend sent me this 2015 report below, which mentions 
the SAME strange observations that I believe I read in Living Bird -- with 
minor differences: this report mentions chicks as nightly departing foster 
nests after sunset, not 3am, BUT returning only at dawn; also, it says the 
nightly escape is solitary, NOT to congregate with other young cowbirds in a 
'teenager party' as I remember from Living Bird (which also said that the field 
congregation was only revealed to Science after new tracking that was launched 
only once researchers had found that the cowbird chick they monitored was 
missing from its nest at night! So, maybe the 'teenager party' was only found 
out after simultaneously tracking several youngsters?)  

Anyhow, here goes:

Science News

Juvenile cowbirds sneak out at night
Date:    November 2, 2015
Source:    University of Illinois at Urbana-Champaign

A new study explores how a young cowbird, left as an egg in the nest of a 
different species, grows up to know it's a cowbird and not a warbler, thrush or 

The study, published in Animal Behaviour, reveals that cowbird juveniles leave 
the host parents at dusk and spend their nights in nearby fields, returning 
just after daybreak. This behavior likely plays a role in the cowbirds' ability 
to avoid imprinting on their host parents.

"If I took a chickadee and I put it in a titmouse nest, the chickadee would 
start learning the song of the titmouse and it would actually learn the 
titmouse behaviors," said Matthew Louder, who conducted the study as a Ph.D. 
student with Illinois Natural History Survey avian ecologist Jeff Hoover and 
INHS biological surveys coordinator Wendy Schelsky. "And then, when it was old 
enough, the chickadee would prefer to mate with the titmouse, which would be an 
evolutionary dead end," he said.

Louder is now a postdoctoral researcher with East Carolina University in North 
Carolina and Hunter College in New York.

The imprinting process is widespread among birds and other animals, but brood 
parasites like the cowbird appear to be resistant to imprinting. They will 
imprint on a different species if confined with that species for an extended 
period of time in a cage, but the birds don't appear to do so in the wild.

Cowbird hosts, such as the prothonotary warblers in this study, have their own 
habits and habitats, and seldom choose to live where the cowbirds live or eat 
what they eat. Prothonotary warblers, for example, live in forests and dine on 
insects and caterpillars. Cowbirds spend most of their adult lives in open 
fields and prairies, and while they do eat insects, about three-quarters of 
their diet consists of seeds.

"Among other things, cowbirds have got to learn to eat like cowbirds or they're 
not going to survive very long," Hoover said.

The researchers wanted to test the hypothesis that cowbird moms are the ones 
that lead their offspring out of the forest. There was some support for this 
idea. A recent study from the same team found that cowbird females don't simply 
abandon their eggs in another species' nest. They pay attention to whether the 
young birds survive, sometimes wrecking the nests of birds that kick the 
cowbird eggs out of their nests.

The cowbird females also return to nests where young cowbirds survived to 
fledging age. Cowbird females are often spotted in the vicinity of cowbird 
nestlings, Schelsky said, and sometimes respond (with vocalizations, not food) 
to the nestlings' begging calls.

To track the birds in the forest and prairie, the researchers put radio 
telemetry transmitters on the cowbird nestlings and on adult female cowbirds in 
the forest where the host parents made their nests. The team took blood from 
the birds and conducted genetic analyses to match the juveniles (and their 
radio signals) to their biological mothers.

But tracking the birds, even with the radio transmitters, was next to 
impossible, Louder said. He tried for a year, but was unable to get meaningful 
data. Then study co-author Michael Ward, a professor of natural resources and 
environmental sciences at the University of Illinois, came up with a new 

"He helped construct an automated telemetry system," Louder said. "We put up 
three radio towers, each with six antennas on it, so you have 360-degree 
directional coverage. All three towers track one individual cowbird at a time 
and then move to the next individual."

With this system, Louder could track the location of each study bird every 
one-to-two minutes.

"We were able to watch the juveniles and see if they left the forest at the 
same time as a female and, if so, whether that female was their mom," he said.

"Strangely enough, the juveniles did not follow the females out of the forest," 
Louder said. Instead, they left on their own, after dark, returning only the 
following morning, he said.

"I started seeing this in the data and I thought it was wrong," Louder said. So 
he went to the forest and followed a single juvenile cowbird for one night. The 
bird left the forest in the evening, moving to a rosebush on the adjacent 
prairie. It was out there all night, alone.

"As soon as the sun came up, the juvenile flew back into the forest and to the 
warbler's territory," Louder said. "Without the automated radio telemetry, I 
would have assumed that it had stayed in the forest all night."

The discovery doesn't explain how cowbirds find their way into a cowbird flock, 
where they learn most of their social and survival skills and eventually find a 
mate. But it does offer some insight into the processes that allow young 
cowbirds to avoid imprinting on their hosts, the researchers said.

"Clearly, there's a lot more to these birds than people would have thought," 
Hoover said. "We still have more layers to peel away from this onion that is 
the cowbird."

Story Source:
Materials provided by University of Illinois at Urbana-Champaign. Original 
written by Diana Yates. Note: Content may be edited for style and length.

Journal Reference:
    Matthew I.M. Louder, Michael P. Ward, Wendy M. Schelsky, Mark E. Hauber, 
Jeffrey P. Hoover. Out on their own: a test of adult-assisted dispersal in 
fledgling brood parasites reveals solitary departures from hosts. Animal 
Behaviour, 2015; 110: 29 DOI: 10.1016/j.anbehav.2015.09.009

Cite This Page:
University of Illinois at Urbana-Champaign. "Juvenile cowbirds sneak out at 
night." ScienceDaily. ScienceDaily, 2 November 2015. 

-End quote. 

Magnus Fiskesjö, PhD
Associate Professor, Department of Anthropology, Cornell University
McGraw Hall, Room 201. Ithaca, NY 14853, USA
E-mail:, or:

Affiliations at Cornell University, WWW:
Anthropology Department,
Southeast Asia Program (SEAP),
East Asia Program (EAP),
CIAMS (Archaeology),
Cornell Institute for Public Affairs (CIPA),
Judith Reppy Institute for Peace and Conflict Studies (PACS),
From: John Confer []
Sent: Saturday, April 11, 2020 7:47 PM
To: Magnus Fiskesjo; CAYUGABIRDS-L
Subject: Re: [cayugabirds-l] Cowbirds

I, also, wonder about this report. I've had to handle nestlings for research 
purposes, always with fear and the most care possible. Nestlings don't stay in 
nests any longer than absolutely necessary because nests are depredated by 
raccoon, cat, weasel, skunk, raptors, etc. Nestlings generally can't leave any 
earlier because they don't have sufficient feathers for insulation nor muscle 
strength to move around. Further, since they don't thermoregulate until just 
about the day they leave, they would have a hard time surviving in the lower 
temperatures of night. 3 to 4 to 5 AM is usually the coldest time of the 24 hr 
cycle, often 20-30-40 degrees colder than mid-day. This doesn't makes sense to 

It is a pretty image.


<> on behalf of Magnus Fiskesjo 
Sent: Saturday, April 11, 2020 10:10 AM
To: AB Clark <>
Cc: Michael H. Goldstein <>; CAYUGABIRDS-L 
Subject: RE: [cayugabirds-l] Cowbirds

This message originated from outside the Ithaca College email system.

Hi, I would love to know, and I sure wish I could find that article. I 
definitely recall that it said the cowbird chicks that were studied left their 
nest like 3am to go to the field ("party"), and then came back to the nest 
before dawn, to continue to pretend to be their slave parent's child!

Of course later they'll not sit in the nest any more, and wander around while 
being fed, I've seen that. And yes I am sure you are right about most of the 
other things you noted! I maybe should not have said "teenager", -- that was my 
word choice, not that of the scholars whose research was reported in that 
Living Bird magazine article.  I used "teenager" because the cowbird nightly 
field party seemed to be a ... teenager's dance party.

Maybe someone else knows the URL for the actual article. I can't find it, I 
must have read it in print only.

This rather memorable article also talked about other astounding discoveries 
such as that the catbird is the only bird that can resist the cowbird's 
trickery. Unlike other birds, it said, the catbird will expel every egg that 
looks different from its first egg. So, the cowbirds can only outsmart it by 
laying their egg in the catbirds' new nest before even mama catbird has laid 
her first egg there. If it can, then the catbird will expel her own eggs, one 
after the other. And if the cowbird scheme fails, it might rip up the nest (as 

Magnus Fiskesjö
From: AB Clark []
Sent: Saturday, April 11, 2020 9:30 AM
To: Magnus Fiskesjo
Cc: Michael H. Goldstein; CAYUGABIRDS-L
Subject: Re: [cayugabirds-l] Cowbirds

I wonder if there has been some mis-intepretation either in the article or by 
subsequent readers.  Cowbird young, like other passerines, leave the nest in 
the care of parents (foster or otherwise) and live outside the nest from then 
on.  (OK individuals may hop outside during the day and return at night for the 
day or two over which they fledge.)  Care for cowbirds in the fledgling stage 
lasts a similar time to their relatives, red-winged blackbirds and other 
smallish icterids.  They should be fed and be following or calling to parents 
over the next 12-14 days, not joining older cowbirds.  Teenagers would be 
perhaps yearling cowbirds?  It is later, in summer and fall, when young 
cowbirds are independent of parents, that they flock up with other cowbirds and 

I haven’t heard anything about 3 am gatherings from Meredith or her students.  
Seems pretty dark for any such passerine to be moving.  West and King studied 
them in aviaries and it could be that researchers got up at 3 am to set up and 
be there when singing started to happen.  But in any case, cowbird song 
learning is a fascinating situation where the basic songs are clearly not 
learned from parents during late nestling or early fledgling periods, i.e. 
develop “innately”, but  are socially modified in a number of ways, feedback 
from female cowbirds and from competing male cowbirds both.  West and King 
published several really nice overviews in accessible papers, Scientific 
American or American Scientist, I believe.

By the way, there is at least one video-documented report of a hatchling 
cowbird behaving like cuckoos and butting host eggs out of the nest.

Anne B Clark
147 Hile School Rd
Freeville, NY 13068

On Apr 11, 2020, at 9:11 AM, Magnus Fiskesjo 
<<>> wrote:

This morning, a male cowbird singing, at Salt Point. Never heard that before. A 
very low volume series of thin crispy notes. No clucking, as in some recordings 
of its song.

The bird sat very close, on top of the little pine/fur tree at the lakeside 
fork of the path to the Bluebird Path.

It refused to leave its perch and continued singing even as I stood right under 
the tree.

Ps. the weirdest cowbird research for me was the Living Bird piece reporting on 
how a cowbird knows it is a cowbird, and not a whatever other bird, despite 
being raised by them as slave parents. It was discovered that the grown chick 
gets up at 3am and leaves the slaving foster parents' nest, to go hang out with 
other teenager cowbirds in a nearby field. Next question is, how do hey know 
that they should get out of bed at 3am and go to the field party and get to 
know their cowbirdness?
ps. I could not find the reference to the Living Bird magazine article where I 
read this. I only find this partial account, also interesting but no mention of 
the teenager party:;;sdata=qSkhspt%2BrENXqrmr5gv%2F5EnKw%2Fe8lssr9wjNCqZMaT0%3D&amp;reserved=0

Magnus Fiskesjö
[] on behalf of Michael H. Goldstein 
Sent: Friday, April 10, 2020 8:05 PM
Subject: Re: [cayugabirds-l] Cowbirds

Cowbirds are crazier than you think…check out the research by Meredith West and 
Andrew King on the role of female cowbirds (who don’t sing) in shaping the 
development of juvenile males' song by using rapid wing gestures:;;sdata=XdPriXo%2BzVrVgjdFjNb3Yo%2FXS7Uj3GGF2iCnLCbniu4%3D&amp;reserved=0
 and more generally,;;sdata=xtWADdPzoRH4NXGPX3EgFrRrBFRG%2FfzdG96Ucbrtmmw%3D&amp;reserved=0


On Apr 10, 2020, at 7:49 PM, Peter Saracino 
<<>> wrote:

I was having a cup of coffee looking out the window at 3 male and 3 female 
cowbirds going at the sunflower seeds. As I watched them it dawned on me that 
all of them were raised by foster parents!!!
According to the Lab of O:
"the cowbird does not depend exclusively on a single host species; it has been 
known to parasitize over 220 different species of North American birds".
Crazy, wild stuff.
Pete Sar
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