Wednesday, May 28, 2014

The Brooklyn Botanic Garden Nest and Robin Nest Placement...WHY THERE! Reasoning vs Instinct in Robin Reproduction

       Photo courtesy of Ann Feldman 

The Red-tailed Hawk nest at the Brooklyn Botanic Garden once again sports what looks like one eyass.

When last we met, I published the photos of the Robin's nest under the dam, which brought a number of responses concerning Robins and nest location.

 Just a little refresher, there is the Robin's nest just under the walkway on a metal plate.  It is secured in place by a metal rod.

 So far things seem to be working out alright, but that metal rod is connected on the top to the wheel that opens and closes the dam.  Therefore it either spins in place or goes up or down controlling the "doors" and hence the flow of water through the dam openings or lack thereof.  

Its movement has not dislodged the nest thus far.

 First from Sally of Kentucky....  

 Robins nest in very interesting locations don't they? I wonder about their decision-making. We have a pair that nests around the raptor rehabilitation center I volunteer at. One would think that nesting above a hawk's mew would not be a good location, or above the peregrine's mew. I had our education GHOW on the glove yesterday and the parents were making quite a ruckus at our presence-3 ready-to-fledge babies peeking out over the edge of the rafters of the mew! We even had one nest INSIDE our large flight cage with rehabbing hawks inside it! I know one or two made it out to fledge, but not all...I don't understand their reasoning for nest placement.

Next up Betty Jo of California...

I hope those robins aren't the type of bird that first land on the
ground when they fledge.  I have decided that robins aren't the
brainiest birds around. After meeting the one that nested repeatedly in the center of a 2 story tall Hawaiian tree fern--the nest being progressively tipped as the new fronds un furled. When I was working there the landscaper kept a huge extension ladder nearby so he could carefully slice off each frond as it started to tip the nest.  The homeowner said several times before the babies had been dumped.
Sigh--birds have such a hard time.
Betty Jo

Robins fresh off the nest once they land for the first time don't really have the wing works to fly right away. They just trot around behind a parent learning about looking for food and being fed by the parent, usually Dad as Robin fledglings tend to have a staggered fledge, for several days until they get the wing strength to get some elevation. 

When a young Robin first comes off the nest depending on wind and other variables they can end up going rather far on their first flight.  It is possible they'll be able to make it if things go right.

That said...

Yes, Betty Jo, Robins do most often land on the ground when they first fledge as they tend to be flightless for several days.

Sally said, "I don't understand their reasoning for nest placement."

Betty Jo said, "I have decided that robins aren't the
brainiest birds around."

No ladies, Robins don't appear at least to be the brainiest birds around nor do they do much reasoning when it comes to nest building or  placement early on in their lives.

Whereas our beloved Red-tailed Hawks may take several seasons to come up with workable criteria for placement of a nest, as well as what to use for materials,  and how to build it depending on the environment in which they find themselves if neither has done it before, Robins often don't have that kind of time to be successful adapters.

The average lifespan of a Robin is l.l years.  Many are working completely on instinct when it comes to nest placement, building, chick raising, and all the other life skills as well during their first breeding season.

Only about 45% of Robin nests are successful.  Why?  Well besides the vagaries of nature, weather, predators and the like, many Robins at this time of year are nesting for the very first time  so there is little to no life experience and hence reasoning to help them be successful.  

They are flying blind on instinct.

It appears to me that part of Robin placement criteria is something for the nest to sit on, which can be a branch or some human made ledge and they also seem partial to an eave, a roof, or enough leaves above the nest for some protection.  As we've seen, what is underneath the nest even in the case of Red-tails who nest over streets or near railroad tracks or other hazards doesn't appear as important as other criteria.

If a Robin manages to live through its first nesting season, which can mean raising two or three broods of chicks, or at least trying to, they've acquired enough useful life knowledge which could include what works and what doesn't in nest site selection  that they may well then live five or six more years or longer continuing to learn what works and what doesn't and getting better at it all the time.  

The longest life span in the wild recorded so far is 13 years, 11 months for an American Robin. 

I therefore posit that the nests and behavior that Sally and Betty Jo have observed as well as the one I found under the dam are likely the work of  Robins working on pure instinct as they are young and haven't had the chance as yet to learn  enough about nest building and site selection to make better choices.

They can't reason as they've no experience to help them along the reasoning road.

Though I once saw a scientist give a paper at The Field Museum in Chicago about "luck" being a factor in an individual of a species or even a group of a particular species survival, which may then make a difference in the survival of an entire species.  He sold me.

So no matter how atrocious some of  the decisions these birds have made look, a little luck can  go a long way in helping them be successful.  For instance the young Robins in the nest under the dam just need a little of  the right wind  for just a little while to get them to safety, which as this is a very small dam, safety is not that far from the nest at all.

Fingers crossed.

Donegal Browne

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