Division of Bird Habitat Conservation

Birdscapes: News from International Habitat Conservation Partnerships

Species at Risk

Along the Nectar Trail
by Bob Benson, Bat Conservation International

It was early June in the Sonoran Desert of southern Arizona as I watched several lesser long-nosed bats (Leptonycteris curasoae) enjoy a meal of nectar at a flowering agave. With the aid of a night-vision scope, I witnessed these nectar-feeders under the cover of darkness as they acrobatically danced from bloom to bloom, affecting cross-pollination.

These bats live in caves and abandoned mines of North America's southwestern deserts. They form nursery colonies of thousands of mothers and young in northern Mexico and the extreme southwestern United States. Bachelor colonies are separate and smaller. The arrival of these highly nomadic bats in the Sonoran Desert coincides with agave and cacti blooming cycles, mostly in June and July, when young bats are born and reared.

Long-nosed bats travel in groups and fly up to 30 miles to reach food, with the largest colonies covering as much as 19,000 square miles a night. Groups tend to feed for about 20 minutes, then pause briefly to digest their food before continuing. Amazingly, the bats spend less than one second feeding within the flowering blooms, yet they may come back to a single flower more than 150 times a night.

These bats migrate in the spring and fall between southern Mexico and the United States, relying on the sequential flowering of more than 60 species of agaves and cacti as they travel. Long-nosed bats pollinate both agaves and cacti and are equally important as seed-dispersers for giant cacti, such as organ pipe, saguaro, and cardon.

The bats and their food plants have become so highly interdependent that loss of long-nosed bats could threaten the health of entire desert ecosystems. In fact, one study documented that the seed production of certain agaves drops to 1/3000 of normal without bat pollinators. This is of concern to the tequila industry, because although most agave used in the production of tequila is a managed crop, wild populations of agave provide the genetic material for new varieties.

Long-nosed bats are listed as endangered by the Mexican and U.S. governments. Loss of feeding habitat and roosting caves are the primary threats to their survival. Thousands of bats at a time are killed when their caves are burned by people who mistakenly believe them to be vampire bats.

Through the Partnership for Conservation of Migratory Bats (co-founded by Bat Conservation International, a nonprofit organization dedicated to conservation of bat species worldwide, and the Institute of Ecology at Mexico's National University) people on both sides of the border are beginning to learn to value and protect these bats, and growing numbers of key roosting caves are now being restored and protected. The Partnership is now a model for other Latin American countries and many are following its lead, implementing strategic bat conservation and management plans.

For more information, contact Bob Benson, Bat Conservation International, PO Box 162603 Austin, Texas 78716-2603, (512) 327-9721, bbenson@batcon.org, website www.batcon.org.

Growing Up in a Tidal Marsh
by Bruce Taylor, Oregon Wetlands Joint Venture

Fish researchers on Oregon's south coast are coming up with dramatic new findings about the importance of tidal marsh habitats for juvenile salmon.

On-going studies at South Slough National Estuarine Research Reserve on Coos Bay have documented extensive use of tidal marshes and off-channel rearing ponds by young coho salmon. Fish biologists have traditionally discounted the importance of estuarine habitats for coho, which are listed as threatened under the United States' Endangered Species Act. That view was based on the assumption that young coho salmon paused only briefly in these habitats as they migrated from their natal streams to the ocean. However, trapping of juvenile coho coming out of South Slough's Winchester Creek in southwest Oregon revealed a more complex life history pattern than previously thought.

A portion of the coho fishery moved down into tidal areas almost immediately after hatching, while some spent up to a year in the upper estuarine habitats. Other juveniles remained in the upper watershed for 8 to 12 months before beginning their downstream migration. Those fish lingered in the upper estuary for periods ranging from a week to as much as 6 months.

Juvenile fish that moved into tidal areas early in their life grew almost twice as fast as those reared in the upper watershed. These findings could provide one of the keys to improving salmon productivity, since direct links have already been established between the size of out-migrating juvenile fish and their early ocean-survival rates. Simply put, the bigger the fish as it enters the ocean the better its chance for survival and return to the spawning grounds at the end of its life cycle.

Crucial, then, to increasing survival rates is habitat availability, but after more than a century of diking, filling, and developing tidal wetlands, the amount of habitat available has been greatly reduced. In effect, juvenile salmon have been cut off from much of what would historically have provided some of their most productive habitat.

Partners of the North American Waterfowl Management Plan's Pacific Coast Joint Venture recently restored diked pastures along South Slough to their former function, creating about 50 acres of tidal marshes—a rich source of food for young salmon. "The juveniles we trap in the marshes, their stomachs are just completely full," says Bruce Miller of the Oregon Department of Fish and Wildlife. "They weigh substantially more than those of the same population that we trap in tidal channels. It is directly attributable to their foraging in the marshes. Ten years ago these areas weren't open to fish. Now, they're providing great habitat."

The recovery of endangered fisheries requires the recovery of the habitats they need. In restoring these habitats, all creatures in the food chain will benefit, from insects to birds to humans.

For more information, contact Steve Sadro, Oregon Institute of Marine Biology, Box 5417, Charleston, Oregon 97420, (541) 888-2581, extension 305, research@harborside.com, or Bruce Miller, Oregon Department of Fish and Wildlife, Box 5430, Charleston, Oregon 97420, (541) 888-5515, millerb@fsl.orst.edu.

Running Out of Reptiles
by Rosemary Forrest, Savannah River Ecology Laboratory

National attention has been riveted on the issue of amphibian declines for years and has intensified with each new report of vanishing populations or deformities. However, according to an article in the August 11, 2000, issue of the journal BioScience, reptiles are in even greater distress worldwide than their better known cousins.

These two vertebrate classes are collectively referred to as herpetofauna, but the focus of general concern has been almost exclusively on amphibians. Now, however, scientists are hoping that the general public will recognize what they have long known: reptiles across the globe are affected by many of the same forces as amphibians but with even greater impact. \

The article's lead author, Dr. Whit Gibbons, a herpetologist and professor of ecology at the University of Georgia, said, "Although the amphibian decline problem is a serious threat, reptiles appear to be in even greater danger of extinction worldwide." He said that while studies on both amphibians and reptiles have not been as rigorous as scientists would like, the existing documentation points to a coming crisis situation.

The problem is multifaceted, but habitat loss and degradation may be the largest single factor in reptile loss. For even when part of a habitat is protected, such as a wetland, the surrounding terrestrial habitat needed by semiaquatic reptiles often is not. Conservation biologists hold as a basic tenet of ecology that intact habitat is necessary for species persistence and well-being, but habitat destruction is just the beginning of the problem. Invasive species introduced to new areas can spell real danger for reptiles. Other problems include environmental pollution, disease, and even the simple presence of humans among a fragile population. Cars kill reptiles; cats and dogs hunt reptilian prey; and people take interesting reptiles from their environment or handle them incorrectly.

The commercial use of reptiles is also cited as a cause for declines. The harvesting of reptiles for pets, food, and for use in folk medicines can result in overcollection. This kind of use affects reptiles more than amphibians. Human use is not universally bad, according to Gibbons, but such use should be "sustainable," that is, the population from which individuals are harvested should be able to rebound to at least the same population level.

Global climate changes may also present problems for reptiles, according to the BioScience article, and some population declines have been noted for which a cause cannot be discerned.

Many populations thought to be in decline simply have not been monitored over long periods of time, making evaluation of the problem difficult. Additionally, the clandestine nature of many reptiles and their large home ranges may allow a population to decline without notice.

"The disappearance of reptiles from the natural world is genuine and should be a matter of concern," according to Gibbons. "Current evidence suggests that these declines constitute a worldwide crisis."

For more information, contact Rosemary Forrest, University of Georgia, Savannah River Ecology Laboratory, P.O. Drawer E, Aiken, South Carolina 29802, (803) 725-2473, forrest@srel.edu.