Phoebe Nest is a Total Loss

On the morning of the 28th the Eastern Phoebe that we have on our webcam at work laid a third egg early in the morning. I grabbed this image on my way out the door at 6:53. It is hard to see as the camera was in infrared mode but there are three eggs in the nest.


When I got to work at 8:00, things had changed. There were only two eggs in the nest. The web cam caught this Brown Headed Cowbird stealing one of the phoebe eggs at 7:33.

This was sad to see but even more frustrating was when she came back the next day and destroyed the two remaining eggs. Here's what the nest looks like now.


There is just a little piece of broken shell. Cowbirds have gone after this nest in past years but they have always just added their eggs to the clutch and let the phoebe raise them. Cowbirds are brood parasites. They do not create their own nest, they lay their eggs in other birds nests and let the other birds raise their young.

A first I wondered if what we're seeing here could be an example of Mafia behavior. Research by Jeffrey P. Hoover and Scott K. Robinson shows that cowbirds will retaliate against other species for rejecting their eggs. The researchers showed that birds who rejected a cowbird egg had their own eggs destroyed 56% of the time while those who accepted them only had their eggs destroyed 6% of the time. This is actually a really interesting example of evolution in action. This behavior of the cowbirds helps drive evolution of other bird species in a direction beneficial to cowbirds. They are selecting for those birds who can't tell the cowbird eggs are in their nest while destroying the offspring (and genetic material) of those birds that have figured out what the cowbirds are up to.

This doesn't seem to be what happened in this nest though since it appears that the cowbirds just came in and destroyed the eggs having not laid any of their own first. This could be an example of what Hoover and Robinson call "farming." The cowbirds are trying to create more opportunities to parasitise the nest by making the phoebes start over. We'll see if they do.

I'm very conflicted about this. Nest parasitism is natural. I don't have a problem with it. However, the Brown-headed Cowbird is an edge species. It is a bird that historically hung out on the edge of the forest. It does not like the thick middle of a heavily wooded habitat and so those birds that do not live in edge areas have not had to compete with cowbirds. The problem is that humans simply adore edge. It is our favorite habitat probably owing to our own genetic heritage. We're slowly turning everywhere to edge as we open up forests while at the same time planting trees in open areas. We've allowed the cowbird into areas where it historically has not been and we've pet it into contact with species who have not had to deal with it in the past.

Cowbirds are just doing what they have always done, it is becoming a problem though because we've changed the playing field.

~Kirk

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Phoebe Day 3: No new egg?

I was teaching all morning so I didn't have time to check out our Phoebe Webcam before heading off to a local school. When I returned, I checked the image expecting to see a third egg. Songbirds typically lay one egg per day and do so in the morning. When I checked the camera all I saw was a bird. The phoebe was on the nest.


Or so it seemed. The time stamp on the image seemed to be about 15 minutes off. I waited twenty seconds and refreshed the image but sure enough, it was frozen. I went down to nudge the computer that uploads the images and when I did I could see the live image below.


There are still only two eggs in the nest. Why didn't the phoebe lay a third egg this morning? When I spoke with staff who were on-site all day they indicated that the phoebe had spend much of the day sitting on the eggs and moving them around. It would seem incubation may have begun. Usually birds do not sit on the eggs until all of them have been laid. This way, incubation starts at the same time and they all hatch at the same time. Why start incubation with only two eggs? A usual clutch size is four or even five eggs. Because the old nest in this location fell down, the phoebes had to build a new one. Building a new nest is energy intensive and in some cases can mean a reduced clutch size. Two eggs may be all we get in this nest.

I did notice two male and two female Brown-headed Cowbirds hanging out in a tree very close to this nest. Cowbirds lay their eggs in other bird's nests. There's a good chance that if another egg does appear it will be from a cowbird and not from the phoebe.

Check back to find out. Tomorrow morning should be interesting.

~Kirk

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FLEDGED!

When I came into work this morning there were still little Eastern Phoebes in the nest. An hour later, I clicked on the site again and they were all gone. Now the question is, will the phoebe lay a second clutch of eggs?

My previous question has been answered. According to the Cornell site, the bird's hatch date was May 22. That was 20 days ago which means having the Cowbird in the nest did indeed slow down the development of the phoebes. They usually fledge in 15 to 16 days.

~Kirk

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Phoebe Video Updates

Here's some video updates for all of you following the saga of the parasitized Eastern Phoebe nest. The Brown Headed cowbird continues to grow at an amazing rate. This probably has to do with the fact that it gets a lot of the food brought to the nest. There was some speculation on the Cornell site that perhaps the phoebe chick were dead as they are hard to see. They are not dead. They are just overshadowed by the huge cowbird. In this first video, you can clearly see two of the chicks. The third is partially visible at the bottom of the screen under the cowbird.

In this next video you can watch the Phoebe come back and bring food to the nest. She brings back what appears to be a beetle. It barely fits down the cowbirds mouth. I don't think the phoebe chicks could have eaten it with their smaller mouth.

This next video shows that the phoebe chicks are indeed getting food. An adult comes back with food and the video starts with the food already in the cowbird's mouth. The phoebe then takes it out and decides to give it one of the other chicks instead. When the cowbird gets up on the edge of the nest you can really see how big it is. It is the same size, if not larger, than the adult phoebe.

Here's another video of the adult feeding a phoebe chick instead of the cowbird. They are still getting food! I think the cowbird was just full. It doesn't even try to get the food in this one.

That's it for videos today. I missed capturing video of the cowbird flapping its wings and stretching. According to The Birder's Handbook, Brown headed cowbirds fledge at 11 days. We're at 11 days today so hopefully the cowbird will leave the nest any time now. In the past I have noticed the phoebe young fledge in the morning so maybe that is the same with cowbirds. If so, hopefully the cowbird will be gone tomorrow and the parents can start focusing on raising the phoebe chicks.

~Kirk

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Phoebe Video

I finally had some time to capture some real-time video off the Eastern Phoebe Cam. There are three phoebe nestlings and at least one cowbird visible. The other cowbird may be hidden underneath the pile.

In the first video, one of the parents brings a large dragonfly back to the nest. It thinks about feeding it to the nestlings but it is too large even for the cowbird. the second phoebe arrives and it looks like the second bird just decides to take the dragonfly away. (Perhaps for a personal meal?)

The second video is a little higher quality. I messed around with the settings a bit to get a higher quality capture. This video illustrates the central problem with having cowbirds in the nest. The cowbird is already about twice the size of the phoebes and this is only five days after hatching. Look at the size of that mouth! When the parents come back with food they see that huge open mouth and they automatically feed the biggest target. The cowbird is getting most of the food. you can see the three small mouths at the top begging for food. The parent considers giving them some but then feeds it to the cowbird.

There's a little bonus at the end of the second video for those scat0logically inclined blog readers. The cowbird expels a fecal sac. The parent bird picks it up and flies away. This is one way they keep the nest clean. Did you ever notice there are no bird droppings in nests? By carrying away fecal sacs, the parents keep the nest clean. Now you know.

It makes me glad to be a human. I may have to change my son's diapers but I don't do it with my mouth.

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Phoebe Nest Update

The Memorial Day holiday took me away from web access which of course means the eggs in the Phoebe Nest have hatched. According to co-workers who were in on last Friday, that is when the action first started. I was so busy today I didn't have much time to check on things but now several (if not all) of the eggs have hatched. I was able to grab a two random shots during the day, the morning one above and the afternoon one below. Sorry, they aren't the best. In the top photo I can clearly make out two birds for sure. It will be really interesting to watch over the next two weeks to see how the phoebe nestlings do with two huge fast growing cowbirds in the nest. Here's one of the parents bringing back some food. Much better pictures will be coming in the next few days. I may also monkey with the feed a little to see if we can get a little crisper image.

~Kirk

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Uh oh: 7 eggs

I've been away from the office for a couple of days and when I returned, my co-host Paul pointed out we now have 7 eggs in the phoebe nest. This is not news to celebrate. Two of the eggs are not from the phoebe. As mentioned in a previous post, there are Brown Headed cowbirds about. A cowbird has visited the nest early in the morning for two days in a row and laid one egg each morning. It happened very quickly and it appears as though the cowbird may have kicked the phoebe off the nest to do it. I took the time lapse feed and slowed it down right when the event happened. It is unfortunately a little pixelated when the action takes place as the stills are taken from a compressed flash video of the feed. Cornell could probably make a clearer video with the raw data we send them. It is not archived locally on our end though so that wasn't an option. The video starts with the phoebe on the nest at 5:21 am. Every frame of the video is 20 seconds. The entire egg laying appears to take about 60 seconds.

We aren't going to remove the egg and neither is the phoebe. Phoebes are acceptors of brood parasite eggs. She will raise them as her own. This will probably mean a few of her own young will die. We won't remove the eggs as it is illegal to do so. Even though people don't like cowbirds, they are a protected migratory species. There's also some research to suggest that removing the eggs may do more harm than good as Cowbirds may engage in what has been termed "Mafia Behavior" Basically they check on the nests they have laid eggs in and if they find them missing they destroy the nest.

This seems to fly in the face of the popular theory that cowbirds evolved into a nest parasite because they followed herds of bison and couldn't stop to nest. If they were dropping eggs and running to catch up with migratory bison then they couldn't come back to check on nests and their eggs. Birdchick has a great excerpt from Alvaro Jaramillo on her blog in which he notes that the Brown-headed Cowbird evolved from South American members of the Molothrus genus and there are no bison in South America. Cowbirds were brood parasitic birds long before they started hanging out with bison.

It will be at least be interesting and educational to watch what happens once the eggs start to hatch. I'll be sure to keep the blog updated.

~Kirk

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Day four: Egg Four

I came in to work early this morning expecting to see the fourth egg in the Eastern Phoebe nest and instead saw this.


Momma bird was still on the nest. Was she still working on the egg? When Paul came into work I commented that she was still on the nest and he said he had seen a Brown-headed Cowbirds right by the nest in the morning. Brown-headed Cowbirds are brood parasites. They lay their eggs in other birds nests and then abandon the young to be raised by the foster parents. Was the phoebe staying on the nest because she saw the cowbird?

I checked again an hour or so later and the phoebe was gone but sure enough, day four and there is a fourth egg.



~Kirk

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