At the risk of making this a longer-than-wanted discussion, I will briefly 
answer—and then retreat!

 I just read Magnus’  report on Louder et al’s study from U Illinois and 
downloaded the actual paper and here is the story.  No one is leaving at 3 am!  
Or flying out of a nest as a nestling.  Too much fine grained terminology is 
leading to misunderstandings, but it is a fascinating paper.

SO—the question that the researchers were interested in was whether actual 
biological mothers of young cowbirds were somehow leading their own fledglings 
away from the Host-parents territory.  The answer is NO.  But the FLEDGLINGS 
(juveniles that have left the nest and are flying, at about 10-20 days old) are 
often leaving on their own, at dusk, to ROOST (sit in the dark) away from their 
foster-parents territories, but still returning to those territories in daytime.

The confusions come in because they put the little radios on the cowbird young 
on about the last day when they were still in their host-nests as NESTLINGS, 
but the observations they report were all on FLEDGLINGS, young that had left 
their nests, never to return.  In Icterids, nestlings do not leave flighted, 
but they can flutter and can cling and climb with strong well developed legs.  
From what I remember, young cowbirds develop a little faster than some.  So 
maybe they fly as early as 5-6 days after fledging—I have to check. 

 But it is during the later FLEDGLING stage, out of the nests and mobile, that 
they start to disappear off foster-territory in the evening.  Sunset isn’t 
dark, so they can still move easily;  apparently motivated by whatever gets a 
cowbird to become a cowbird, they often left to roost alone, during the next 3 
weeks of still being associated with foster-parents during the day.  And their 
non-doting cowbird mothers don’t have anything to do with it, because they were 
also being tracked by radios and triangulating receiver towers, and 
mom-cowbirds were not present during these movements.

Did it bring juvenile cowbirds into contact with other cowbirds?  Apparently 
not, at that stage.  But the “go away, young man/cowbird” urge was already 

So thanks, Magnus, for bringing our attention to this really interesting 
report!  (I can send it to anyone who wants to read it!)


Anne B Clark
147 Hile School Rd
Freeville, NY 13068

> On Apr 11, 2020, at 10:02 PM, Magnus Fiskesjo <> 
> wrote:
> 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 sparrow.
> 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 approach.
> "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. 
> --sincerely, 
> 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 me.
> It is a pretty image.
> John
> ________________________________
> From: 
> <> 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 revenge).
> --yrs.,
> 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 blackbirds.
> 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
> 607-222-0905
> 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:
> --
> Magnus Fiskesjö
> _________________________________
> From: 
> [] 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:  
>  and more generally, 
> Cheers,
> Mike
> 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
> --
> Cayugabirds-L List Info:
> Welcome and 
> Basics<;;sdata=YBc0zAbfcuHW45Yx%2FhymfcgRYopgrTX5HMU5zg%2FBbVg%3D&amp;reserved=0>
> Rules and 
> Information<;;sdata=X7cYv2R5jFMSYzlJNv9q%2BOekd4cpB2oRFAjIXXnJK6o%3D&amp;reserved=0>
> Subscribe, Configuration and 
> Leave<;;sdata=OTXEy%2BMxvrLK%2FmrIIj1o1JUT%2BSL3urVy9nKmsZ1Ax1Q%3D&amp;reserved=0>
> Archives:
> The Mail 
> Archive<;;sdata=ZLdytExR8Ou9bonGHjUJsyGxP2doQcZ37A%2FAZf8lLg8%3D&amp;reserved=0>
> Surfbirds<;;sdata=AdNsZB5WT9MUfdgTZVUqvfBmk4HIfPvM%2F1cX66HjaHM%3D&amp;reserved=0>
> BirdingOnThe.Net<;;sdata=XIBFK84URmGy2dU%2BZm9mKQ1%2Fu9iM1o2NnhF6VkpVy0w%3D&amp;reserved=0>
> Please submit your observations to 
> eBird<;;sdata=ZTwmUkGnF%2F0S0AtZ%2FqtFYoHFPUa82bPdgsYQJ%2BKNYAM%3D&amp;reserved=0>!
> --
> _______________________________________________________________
> Michael H. Goldstein
> Associate Professor
> Director, Eleanor J. Gibson Laboratory of Developmental Psychology
> Director, College Scholar Program
> Department of Psychology, Cornell University
> 270 Uris Hall, Ithaca, NY 14853
> Office 607-793-0537;  Lab 607-254-BABY;  Fax 607-255-8433
> Cornell B.A.B.Y. Lab:  
> _______________________________________________________________
> --
> Cayugabirds-L List Info:
> 1) 
> 2) 
> 3) 
> Please submit your observations to eBird:
> --
> --
> Cayugabirds-L List Info:
> 1)
> 2)
> 3)
> Please submit your observations to eBird:
> --


Cayugabirds-L List Info:


Please submit your observations to eBird:


Reply via email to