Migration takes guts

July 07, 2003

KINGSTON, R.I. - July 7, 2003 - When birds migrate over long distances to and from their breeding grounds, it takes more than strong flight muscles and an innate knowledge of where they're going. According to a University of Rhode Island researcher, migration also takes guts.

Several studies conducted by URI physiological ecologist Scott McWilliams have shown that birds have a flexible digestive system that they modify to meet the changing energy demands of migration.

"The gut of a migratory bird is a really dynamic organ. In preparation for migration, the gut increases in size tremendously over several days," McWilliams said. "It expands, its cells get larger and it produces new cells so the bird can dramatically increase its food intake and store up energy for the long flight."

But because the digestive system is one of the most metabolically active tissues in the body and it consumes a great deal of energy, it shuts down during migration so more energy can be diverted to fueling flight. This partial atrophy of their digestive system affects birds when they stop to feed at sites along their migration route. McWilliams says that because their digestive system is shut down, the birds must eat less until their gut becomes acclimated and can operate efficiently again.

"We've known for many years that birds recovering from a migration flight do not immediately regain body mass, but we didn't know why. Now it's clear that this digestive constraint is responsible for the delay and likely affects the pace of a bird's migration," said the Kingston resident.

One important result of McWilliams' research is a new understanding of the protein requirements of migratory birds. Ornithologists have long believed that a diet high in energy was all that was necessary to sustain migratory flight. But the URI researcher said that proteins are also needed to build the digestive tract. This need for protein may have a significant impact on habitat management at key migratory stop-over sites.

"To build their digestive tract, birds need foods available in the environment that have sufficient protein," McWilliams said. "When birds feed only on fruits that are high in fat and low in protein, they may have to delay their migration. To help birds ensure a successful migration, we need to ensure, for example, that shrubs along their migratory routes have fruits with higher protein amounts."

Little is known about the nutrients in wild fruits, so McWilliams' current research is aimed at identifying the shrub species that bear fruit with high protein and energy content.

Funded by the National Science Foundation and the U.S. Department of Agriculture, and with logistical support provided by The Nature Conservancy, McWilliams' field studies have involved both free-living and captive birds, mostly white-throated sparrows, red-eyed vireos and yellow-rumped warblers. He and his students work each fall on Block Island, R.I. measuring the dynamics of body mass, body composition and gut size of wild songbirds as they stop there during migration. Using experiments with captive birds, he has also examined the physiological effects of short-term fasting, which most birds experience during migration, and then observed the feeding delay that occurs when the birds were then allowed to eat as much as they wanted.

McWilliams began studying the physiology of birds as a graduate student at the University of California at Davis in the early 1990s. He joined the faculty of URI's Department of Natural Resources Science in 1998 after a three-year postdoctoral fellowship at the University of Wisconsin at Madison.

"Migration is very costly to birds," said McWilliams. "But just like people who exercise to modify aspects of their bodies, birds can modify their bodies too so they can accomplish the formidable feats of endurance required by migration."
-end-


University of Rhode Island

Related Protein Articles from Brightsurf:

The protein dress of a neuron
New method marks proteins and reveals the receptors in which neurons are dressed

Memory protein
When UC Santa Barbara materials scientist Omar Saleh and graduate student Ian Morgan sought to understand the mechanical behaviors of disordered proteins in the lab, they expected that after being stretched, one particular model protein would snap back instantaneously, like a rubber band.

Diets high in protein, particularly plant protein, linked to lower risk of death
Diets high in protein, particularly plant protein, are associated with a lower risk of death from any cause, finds an analysis of the latest evidence published by The BMJ today.

A new understanding of protein movement
A team of UD engineers has uncovered the role of surface diffusion in protein transport, which could aid biopharmaceutical processing.

A new biotinylation enzyme for analyzing protein-protein interactions
Proteins play roles by interacting with various other proteins. Therefore, interaction analysis is an indispensable technique for studying the function of proteins.

Substituting the next-best protein
Children born with Duchenne muscular dystrophy have a mutation in the X-chromosome gene that would normally code for dystrophin, a protein that provides structural integrity to skeletal muscles.

A direct protein-to-protein binding couples cell survival to cell proliferation
The regulators of apoptosis watch over cell replication and the decision to enter the cell cycle.

A protein that controls inflammation
A study by the research team of Prof. Geert van Loo (VIB-UGent Center for Inflammation Research) has unraveled a critical molecular mechanism behind autoimmune and inflammatory diseases such as rheumatoid arthritis, Crohn's disease, and psoriasis.

Resurrecting ancient protein partners reveals origin of protein regulation
After reconstructing the ancient forms of two cellular proteins, scientists discovered the earliest known instance of a complex form of protein regulation.

Sensing protein wellbeing
The folding state of the proteins in live cells often reflect the cell's general health.

Read More: Protein News and Protein Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.