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Designing a Spider Web to Evade Bird Collision

The spider’s hard work often takes the hit
© Adedotun Ajibade - Flickr CC View Large

One of the lesser known hazards of a bird’s life — when flitting from shrub to shrub — is collision with spiders’ webs. And when a bird flies through a web, it’s the spider’s hard work that takes the hit. It can take a spider an hour just to repair the damage and get on with the task of snaring its next meal. Some spiders have evolved a behavior to give birds advance warning of their webs. They weave into the structure visible designs of white, non-sticky silk, called stabilimenta. These make it easier for birds to see it — and avoid it.

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Transcript: 

BirdNote®

How Birds Dodge Spider Webs

Written by Bob Sundstrom

This is BirdNote.
[Deciduous forest ambience]
One of the lesser known hazards of a bird’s life, flitting from shrub to shrub, is collision with spiders’ webs. Some birds run this gauntlet daily. And when they fly through a web, it’s the spider’s hard work that takes the hit. It can take a spider an hour just to repair the damage and get on with the task of snaring its next meal.
So some spiders have evolved a behavior to give birds advance warning of their webs. They weave into the structure visible designs of white, non-sticky silk, called stabilimenta. [singular: stabilimentum] These make it easier for birds to see it – and avoid it.
Scientists studied the behavior of a common spider called the Black-and-yellow Garden Spider, that weaves a web of up to two feet in diameter. These spiders build visible stabilimenta (pronounced stay-bill-i-MEN-tuh) into their large webs – but only sometimes. When they do, bird collisions drop by nearly half. On the other hand, prey capture drops by a third, perhaps because the stabilimenta also warn off some insects.
    So there’s a cost/benefit trade-off for the spider. Just what triggers a spider to spin its web one way or another, though, isn’t fully known. But since they often weave a new web every day, there are many opportunities to vary their tactics.
[Deciduous forest ambience]
For BirdNote, I’m Mary McCann.
                                                                               ###
Ambient sound: ‘Deciduous Forest Country Morning’, Track 46, NatureSFX recorded by Gordon Hempton of http://quietplanet.com
BirdNote’s theme music was composed and played by Nancy Rumbel and John Kessler
Producer: John Kessler
Executive Producer: Dominic Black
© 2016 Tune In to Nature.org   May 2016   Narrator: Mary McCann

ID#                 spider-01-2016-05-12    spider-01

STUDY:
http://beheco.oxfordjournals.org/content/10/4/372.full

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