Osprey:Sibling rivalry, cainism, cannibalism and moving carcass around the nest-video (1 Viewer)

Just to show how weather and food shortage (that more likely was related to a brutal weather - Osprey parents could not find enough accessible fish) can impact life in the Osprey nest check this video taken this spring.

http://www.youtube.com/watch?v=UwLComEfalk

And an important note: this particular Osprey pair had no problems during last 5 years fledging even 3 chicks during two different years. Female almost never hunted during nesting seasons in past years – this year she was providing at least half, if not more fish than male, and the pair was only able to raise one chicks that was often left alone for many hours as both parents were trying to catch fish at that time. Two younger chicks did not survive sibling rivalry and died from starvation, dehydration and probably overheating. I don’t expect anybody to enjoy watching this video, quite appositive, but I think it is interesting to see the event that is very rare to witness in person. I know only about one documented case of Osprey cannibalism. Brood reduction - cainism (siblicide – obligate and facultative) is well documented in raptors (and not only), but again, rarely witnessed. There are 4 major hypotheses trying to explain sibling aggression and siblicide: The Food-Amount Hypothesis (FAH) - the most generally accepted hypothesis, the Prey-Size Hypothesis, the Brood-Size Hypothesis and the Challenge Hypothesis. All have been supported by evidence but, however, no single hypothesis can fully explain the cause of avian siblicidal aggression. At least I could learn a lot this year when collecting observations during atypical weather/food accessibility conditions.


A few still photos illustrating the Osprey cainism are in a few folders here:
http://www.pbase.com/mbb/from_the_field - I should add more photos in the near future.

Best,

Mark

Mark thanks for the video....yes, depressing, but very helpful in understanding how they act under environmental stresses. I've seen the result of cainism but haven't ruled out exposure as a possibility also. THe fledgling had peck marks and was emaciated...little more for me to conclude as I don't have a way to get nest level and observe. This year was depressing here as at least 2 dozen nests were destroyed in the April 27 tornado outbreaks. Plenty of food, they just have to start over and many lost mates. Any sign of non-fish dietary selection when they are under stress? I'm just working a hunch in case you observed it.

Thanks Lashinala for you interesting comments - it is very bad year for many of us - people and birds. I was watching and thought about it but only the fish was taken. Although once the male brought fish that he probably scavenged somewhere. Also a few times when female was hungry she was digging up some few days old pieces of fish that was very hard to eat (catfish) and tried to get something edible out of them.

All the best,

Mark

Mark B Bartosik said:

Thanks Lashinala for you interesting comments - it is very bad year for many of us - people and birds. I was watching and thought about it but only the fish was taken. Although once the male brought fish that he probably scavenged somewhere. Also a few times when female was hungry she was digging up some few days old pieces of fish that was very hard to eat (catfish) and tried to get something edible out of them.

All the best,

Mark

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Very interesting comments. I am not clear if the second chick died or not.

As far as canibalism is concerned I have seen one example. At the DPOF nest in 2004 the 4th chick died and next evening Betty fed it to the remaining chicks the following evening. That video should still be available but I will not not post it unless people want to see it.

In 2006 times were very hard in the DPOF and the little one Flag was only saved by Betty going to fish. Just before that Flag had a cunning plan to get a meal. See here

However the crisis went on and on and Flag took 66 days to fledge...longer than any chick I have known except in Australia where there is not the same pressure to get airborne.

I am fascinated by your comments about the female being forced to go fishing. We were just discussing that the other day.

Tiger_mz said:

Very interesting comments. I am not clear if the second chick died or not.

As far as canibalism is concerned I have seen one example. At the DPOF nest in 2004 the 4th chick died and next evening Betty fed it to the remaining chicks the following evening. That video should still be available but I will not not post it unless people want to see it.

In 2006 times were very hard in the DPOF and the little one Flag was only saved by Betty going to fish. Just before that Flag had a cunning plan to get a meal. See here

However the crisis went on and on and Flag took 66 days to fledge...longer than any chick I have known except in Australia where there is not the same pressure to get airborne.

I am fascinated by your comments about the female being forced to go fishing. We were just discussing that the other day.

Click to expand...

First I think this question was directed to me (“I am not clear if the second chick died or not.”). Shortly: there were 3 hatchlings – C3 (youngest) died from starvation soon after hatching, C2 last moments were shown on video, C3 survived and just fledged at age of about 65 days. Took little more than last year when 2 chicks fledged when about 60 days old (3rd egg didn’t hatch) but there was no shortage in food supply. Yes northern (migratory) birds usually fledge earlier than non-migratory Ospreys from southern populations. BTW 66 days is longer than usual but hardly a record, and one does not need sail to Australia; Judge (1983) reported minimum fledging time in Gulf of California (non-migratory) 52-76 days. In all populations, brood size, food supply, weather, etc are factors that can impact the fledging time.

You mentioned a case of Osprey cannibalism (“As far as canibalism is concerned I have seen one example. At the DPOF nest in 2004 the 4th chick died and next evening Betty fed it to the remaining chicks the following evening.” – I assume you watched video and did not witness the act in person) that is the recorded case I mentioned in my original post above without going into the details. I noticed that many people avoid not only posting some interesting behaviors (like cannibalism) but also avoiding accepting the reality of life and trying to keep idealistic images of some animals chosen as sort of their icons (this not applied to your comment). Ospreys are only known to eat dead fish in very hard times. Cases of cannibalism seem to be extremely rare. I am sure one can find many more cases of human cannibalism (even in present time) – just google it. BTW even Dennis Puleston ate human flesh together with cannibals in New Guinea.

Perhaps the best example when many people do not accept the true nature of their iconic bird is Bald Eagle. A thief that can be found most easily on landfills feeding on rotting leftovers. But it is very photogenic bird (not on landfill) and like the lion (another good example of choosing a wrong character) became a symbol of values they do not posses. BTW in many other eagle species cainism is obligatory (that means that in almost all cases only one chick would stay alive).

And just a few extra words about sibling aggression in Osprey populations as I am working on putting together videos/photos that are showing some interesting details of this behavior. It can be little misleading if one will only read a few selective papers as different authors present often only limited data and descriptions will not apply to every possible scenario. Examples. There is published record of very young chicks that will stop aggression when about 3 weeks old, another author observed that nestlings will start be aggressive toward end of the nesting time and others, often, observed broods where no aggression were noted. After reading all published papers it becomes quite clear that there is no one universal scheme. And, as I collected a lot of evidence (videos/photos) of sibling aggression (or lack of it) during all stages of young Ospreys before fledging I hope that I will be able to show interesting information. In last video, by purpose, I omitted the photos of most aggressive attacks as those can be a little misleading. Adequate food supply seems to play much more important role and I witnessed more violent attacks in the past that ended with breaking skin and bleeding but younger sibling did not have problem to stay in good health and fledge without delays.

Best,

Mark