Protective Nests

nest_JMLandin

Birds nest in trees, on the ground, on water, among cliffs, and in caves. They build their nurseries from plant materials, mud, dung, saliva, spider silk, pebbles, and animal hair. Some nests have roofs or multiple rooms. Some are simple scraped depressions in the earth or natural cavities in trees.

Most songbirds construct cup-shaped nests which require about 1000 trips to bring in building materials (1). The birds use their feet to scrape, chests to push, and beaks to manipulate twigs and grasses as they rotate. Exhausting! Why go to such an extreme effort? Predators. Birds living on predator-free islands nest on the ground.

Some ground-nesting birds have other ways of avoiding predators… like teaming up with defenders. The red-breasted goose of Siberia nests next to peregrine falcons. The geese act as look-outs for foxes; the falcons attack. Some birds build their nests in ant or termite colonies to protect the eggs.

These sleeping bird babies, pictured, are cardinals. Their parents built this camouflaged nest in the crook of a pear tree. If dad hadn’t stopped by with some breakfast, I would have never realized they were there.

  1. Collias, N.E. 1964. The Evolution of Nests and Nest Building in Birds. American Zoologist. 4: 175-190.
Advertisements

Chirpless: Camel Crickets

camelcricket

Camel crickets (Ceuthophilus sp.) enjoy hanging out with humans. Perhaps you provide shelter to some in your garage or basement. These insects lack one major cricket trait though – chirping. Sound production should allow camel crickets to find each other in a dark cave or crawlspace. So, why no chirps?

A Chirp Mystery

One possible reason for the lack of chirps is a high risk of predation. In other species of crickets, those who call more or longer often end up as a snack. 1, 2 While I would hope camel crickets are relatively safe from bats and birds in your basement, spiders and mice are the crickets’ major predators. Both possess a solid sense of hearing.

Many crickets have parasites who also seek hosts by sound. Chirps attract female crickets, but they also draw mama parasites searching for a cozy spot to lay eggs. The developing parasitic larvae eat the cricket from the inside, exploding out of its body as they grow. Crickets in areas with these parasites quickly evolve “chirplessness.” Do camel crickets need to worry about these “Alien” chest-bursting scenes? While they do have a doozy of a parasite (an intestinal parasite that weakens the cricket enough to ensure predation), the infections are not related to sound production.

Perhaps camel crickets simply lost their physical ability to chirp. Most crickets produce sound by rubbing their wings together. Camel crickets, though, don’t have wings. In a basement, flying is probably not the most effective means of transportation.

The Scent of a Cricket

So, how do camel crickets find each other without sound? One word: pheromones.

Pheromones are used by many cricket species to indicate dominance, reproductive readiness, and location. Camel crickets release a scent that causes them to congregate. Researchers determined the pheromone is unrelated to reproduction since juveniles move toward the scent too. Nagel and Cade3 think the pheromone prevents camel crickets from drying out. We do know the antennae detect these pheromones. In a rather disturbing experiment, researchers found that camel crickets don’t aggregate when their antennae are lopped off.

 

  1. Baily, W.J. & Haythornthwaite, S. (1998). Risks of calling by the field cricket Teleogryllus oceanicus: potential predation by Australian long-eared bats. Journal of Zoology. 244(4) 505-513.
  2. Hedrick, A.V. (2000). Crickets with extravagant mating songs compensate for predation risk with extra caution. Proceedings of the Royal Society B 267(1444) 671-675.
  3. Nagel, M.G. & Cade, W.H. (1983). On the role of pheromones in aggregation formation in camel crickets, Ceuthophilus secretus (Orthopter: Gryllacrididae). Canadian Journal of Zoology 61(1).