Why Do Starlings Strut & Bluejays Hop? - 8 Mar 05

Here's what I asked--- 04 Feb 05: Is there an ornithologist in the house? A wide variety of birds steal from the catfood plates I put out on the back porch. The bluejays land on the porch and both feet off the ground at the same time---hop, hop, hop---to the plate. The starlings, though, land on the porch and strut---left foot, right foot, left foot, right foot---to the plate. Is there some difference in leg structure between a bluejay and a starling that would account for this very noticeable difference in their on-the-ground mode of locomotion, or is this purely a matter of culture? If it makes a difference, I live in northern NJ, USA. ---And anybody who thinks bird "tribes" don't have culture hasn't seen the adult bluejays in my neighborhood teach their youngsters precisely which of my cats is a danger to them. "Black cat...no problem." "Yellow cat---FLY! FLY! FLY!" After some ten years of listening and watching, I've grown so used to the jays' "yellow cat" warning call that, on hearing it, I just get up and open the porch door and wait for Sooty Red to climb the stairs and come inside. The jays will tell me where he is even if I can't see him! Here's what Sue L. tells me--- "I'm not an ornithologist, although my bachelor's degree was in wildlife biology. I am, however, a librarian, which means I can find just about any piece of information someone would ever want, even if it's not in my area of expertise. :-) "Regarding your Wishlist item about walking vs. hopping in starlings and blue jays, bird leg and foot anatomy is, as you surmised, at least partly responsible for their differing locomotion styles. The anatomy is strongly tied to how the bird uses the legs and feet for hunting, grasping, perching, etc. "Birds that spend most of their time on the ground walking have larger leg muscles (or drumsticks, if you prefer). For example, ostriches have huge leg muscles compared to their chest muscles, as they do not fly. Hummingbirds have relatively tiny leg muscles and relatively large chest muscles, as they spend all their time either in flight or perched. "The amount of time spent on the ground differs depending on the birds' diet and how prone they are to being preyed upon. "Starlings are primarily insect eaters, but don't catch them in the air. Blue jays are omnivorous, spending more time at various levels above the ground. How birds hunt for food, if they are not strictly seed eaters, is determined partly by how many calories are expended in the hunting vs. the calories gained from the food. If a bird species gets more caloric reward for flying over walking, the individuals will be hoppers on the ground, due to relatively weaker leg muscles. "As far as the likelihood of being preyed upon, if a bird has numerous enemies, there may be a tradeoff toward chest muscles for flying over leg muscles, leading to hopping vs. walking." * I can hear Mabob gronk and I can see his (or her) parrot-like bird face eying me askance, but this is the first time I've ever seen Mabob strut like one of those arrogant starlings on my back porch. Special thanks, Sue, for Mabob's new arrogant strut! *

Unless otherwise noted, all text and photos © 1992-2007 by Janet Kagan