Category: animal behavior

Birds that weave and sew

February 8, 2020 • 1:30 pm

Here are a few videos of the amazing behaviors of some birds—birds that sew and birds that weave. After you see these, perhaps you won’t see the term “birdbrain” as pejorative.

Here’s Orthotomus sutorius, the Common Tailorbird (not common in any way), a warbler-like passerine that lives in tropical Asia.  It has a stunning way of building a nest. First it takes a big leaf, pierces it with holes, and then, using plant fiber, sews the edges of the leaf together, making a cradle or cup inside which the real nest is constructed. It’s a way of both protecting and camouflaging the nest.

The first video below was sent to me by Bruce Lyon, who shows it in his ornithology classes at UC Santa Cruz. He was responding to my puzzlement about how this behavior evolved. It’s a certainty that the instructions for building this nest-cradle are genetic, instilled in the bird’s brain by natural selection. But for that to happen, there has to be some beginning behavior that is adaptive, and then that evolved into the complex procedure we see today after a gradual and sequential refinement of that initial behavior. For natural selection to have built this, each step of the evolutionary process had to confer a reproductive advantage on the bird. I couldn’t figure out what the initial step was, for it would have had to lead to piercing the leaf and sewing it together; and how did that evolve? I have no idea.

I suppose the ID morons could use this as an example of “irreducible complexity”, for the behavior doesn’t appear to be adaptive until the complex procedure has already evolved. But I’ve learned enough in my years as an evolutionist to realize that this is a limitation not on nature, but on our imaginations. So many behaviors whose evolution has appeared mystifying have, upon later study, revealed incipient stages that one could envision evolving via natural selection into something more complex. (Darwin talked about this in The Origin when pondering the construction of beehives with hexagonal wax combs.)

Perhaps readers of an ornithological bent can posit how the tailorbird behavior got started. Regardless, what we see now is something amazing.

Here’s a longer video (nearly a half an hour) if you have the patience and want to see the whole process:

Weaverbirds don’t sew but weave, but that’s no less remarkable, for their weaving involves tying knots—good ones. This is easier to envision; as Bruce said, “The knots are easier for me to think about incipient stages — lots of birds wrap strands of vegetation around branches to anchor the strand.”  And it’s the males who build the nest, trying to lure females with their architectural prowess. 

And voilà: we get this (there are three videos; the first emphasizes knot-tying:

Here’s the whole process, starting with the knots and continuing with the weaving.

 

More knots and weaving.

 

 

Reader’s wildlife videos

February 1, 2020 • 8:00 am

Tara Tanaka (Vimeo page here, Flickr page here) has graced us with two more of her videos, one very short. (I’ll see her, her famous blind, and her wetlands, the site of many of her videos, in March when I give a talk in Tallahassee.) Tara’s captions are indented, and be sure to play the videos on big screen with sound.

First, a short one: “They’re back!” from January 25:

On 1/6, the only Great Blue Herons [Ardea herodias] we had in the swamp were our winter Great Blue Heron and one new arrival. Within the last week, at least 20 other Great Blues have arrived, and it appears that most of them have found mates and that they’re building nests. I was in the blind the other morning and suddenly saw about 20 birds flying chaotically from the area of the nest trees and into the open where they all landed in tall cypress trees that surround the swamp. I’ve never seen 7 Great Blues in one tree before, but on this morning there were 7 at one time in the tallest cypress before they slowly started returning to the privacy of the interior of the swamp. This tree is approximately 700’ from my blind.

And a longer video, posted yesterday:

In early June 2019, when some of our young Wood Storks had already fledged, two pairs of storks surprised us with two hatchlings, each in a tree that we could see from the living room window. These were the first nests we could see from the house, and it was quite a treat to get to watch the little guys grow up, and I even videoed their first flights and shaky landings. I had much better views of these nests from a vantage point to the east of the nest, which is where I videoed the parents and then the adorable little nestlings when I shot the clips in this video.

Last week, as I videoed a Great Blue Heron landing in the top of a cypress, I realized that it was the stork’s nest tree that I’d watched for months. This heron made multiple trips to this and another tree to recycle nest sticks that the storks had worked very hard to collect last year. Wood Storks are very large birds, and they frequently land in a large water oak in our backyard to get nest material. They feel branches with their beaks for just the right size and flexibility, and then throw their weight back to break the branch, using their wings for balance.

In the past I don’t remember the nests being so intact the following year, but we didn’t have any hurricanes or tropical storms last year, and most of the nests look to be in almost as good shape as when the birds fledged last summer. I can’t help but wonder if there are any birds that might use some of the old nests this season – if the herons don’t completely deconstruct them. Last year we had quite a few Great Egret nests that had incubating birds that were taken over by Anhingas – hopefully they’ll use some old stork nests this year and leave the egrets alone.

 

Readers’ wildlife photos: Stunning animal architecture

January 28, 2020 • 8:00 am

Nicky Bay is a superb photographer of small animals. I don’t think he’s technically a “reader” of this site, but I wanted to put his pictures under this category. Nicky has a Flickr site here, a Twitter page here, and a website, Macro Photography in Singapore, here. I’ve featured his photography three times on this website (here, here, and here).

He recently had a wonderful post called “5 Mysterious Structures From The World’s Smallest Architects,” but I’ll give the link below the fold. First I want you to guess what kind of creature made these structures. Nicky let me use the photos, which are copyrighted and cannot be reproduced without permission.

1.)  A log cabin made of twigs:

2.) A “jungle tent” made of leaves:

3.) Cage fortress!

4.)  Poop barricade!

5.) Web tower. 

Click on “read more” to see the answers:

Continue reading “Readers’ wildlife photos: Stunning animal architecture” →

Juvenile striped eel catfish form a coordinated, roiling ball to avoid predation

January 27, 2020 • 1:15 pm

Both Matthew and reader Dom sent me this link to The Colossal describing and showing another amazing animal behavior, this time in the striped eel catfish (Plotosus lineatus), a smallish species (average size about 14 cm) found in the Indian and Pacific Oceans, as well as the Mediterranean where it’s a recent invader. It’s the only catfish associated with coral reefs.  It’s also venomous, with a poison spine on the dorsal fin and each of the pectoral fins, which is reported to have been “fatal”, apparently to at least one human.

While adults are solitary or occur in small groups, the juveniles form schools like the one shown below, comprising 100-150 individuals.  As the report below recounts (click on screenshot), and the videos underneath show graphically, the youngsters swim in roiling balls of fish, with each individual heading towards the bottom and then back up again. (The video was filmed in Bali.) They apparently gather like this for protection, as younger fish are only lightly venomous and could be taken by predators who apparently avoid adults. (Note the striking striped coloration, which may well be “aposematic“: a pattern warning that the bearer is dangerous or distasteful.)

Why they move down and up again is anyone’s guess. I had two ideas: it gives everyone a chance to forage on the bottom while they stay together as a mass, or it makes their pattern more obvious to predators. Or it could be both.

The video comes from the Abyss Dive Center in Bali:

I found another two-minute video that also suggests that they move like this so all individuals can forage.  And be sure to see what happens one minute in, when they rise from the sea floor all together, writhing like a giant jellyfish:

Here are two photos from the Monaco Nature Encyclopedia. The first is an adult, the second a school of juveniles hiding in a reef.

© G. Mazza

 

© Sebastiano Guido

A tweet: amazing behavior of ants and termites

January 27, 2020 • 11:30 am

Posting may be light today as I had to spend much of the morning in the Social Security Office securing a replacement card. These offices could be called the Waiting Room to Hell, because they’re crowded, ugly, uncomfortable, and the wait is long, even with an appointment. (A logistic error on their part made it impossible for me to order a replacement card online.) Anyway, here is a cool tweet.

This was sent by reader Paul, who wondered whether it was real or faked. I checked and it apparently is real, so I present it to you as a “scientific” fact that is provisionally true. It’s one of the most incredible pieces of insect behavior I’ve ever seen, with two ranks of soldiers, each guarding a column of workers, facing off peacefully—and from two species residing in entirely different orders of insects (Hymenoptera and Blattodea).

Look how evenly spaced the termite soldiers are! In contrast, the ants are slovenly.

Sequential shell swaps in hermit crabs

January 23, 2020 • 2:30 pm

Here’s another Attenborough video featuring the lifelong attempts of hermit crabs to find shells that fit them as they grow. A hermit crab without a shell is a pathetic thing (see several at 2:39), easily taken by predators or cooked by the sun. Here’s a stunning behavior in which a line of crabs forms in order of size, with the aim of each one swapping up to a bigger shell within a matter of minutes. Or course, the biggest crab needs an empty bigger shell to move into, which apparently is the case here. The picture of the lineup at 1:32 is fantastic.

The video comes from “Life Story,” part of the great BBC Earth series.