The who's who of spotted owls

Genetic diversity is one of several aspects of spotted owl biology that Los Alamos scientists hope to better understand with the aid of data gleaned from the field. The study, which also will provide valuable information about the birds' habits to wildlife researchers interested in stabilizing endangered species population, will use genetic information derived from a particularly noninvasive technique: The DNA has been acquired from feathers collected from the owls' habitat.

The team has extensive experience studying bird genetics and has developed a method of analyzing the DNA characteristics of the Jemez Mountain owls and of tracking their habits by collecting and analyzing their feathers.

The Mexican spotted owl was listed as federally threatened in 1993. This subspecies of the spotted owl is found in northern Arizona, southeastern Utah and southwestern Colorado, south through New Mexico, west Texas and into Mexico. The Mexican spotted owl generally inhabits mixed conifer, pine-oak and riparian habitat in mountains and canyons.

The U.S. Fish and Wildlife Service's recovery plan for the subspecies requires research on population biology, gene flow and genetic isolation of populations. To gain such information in the past, researchers needed to capture and handle the birds to take blood or tissue samples. By studying feathers the birds have molted in and around their nests, scientists have eliminated concerns of hurting the owls or changing their behavior.

The Los Alamos team has collected more than 1,300 Mexican spotted owl feathers from 19 identified territories in the Jemez Mountains over the past 17 years. They now have a database of feathers: Each one has been photographed and given a number for tracking purposes, then placed in a bag to ensure no cross contamination occurs.

In the lab, the feather DNA is isolated for analysis. The end of a feather is diced up and placed in a solution that ruptures the cells and releases the DNA. After eliminating the proteins and other contaminants, the relatively pure form of DNA that remains looks like water. The sample is examined for a specific set of repetitive sequences, usually one to six base pairs repeated over and over. These sets of repeats are known as microsatellites.

The team has constructed a library from a DNA sample of a Mexican spotted owl housed in a rehabilitation center in Albuquerque. The library provides a way to archive a series of DNA fragments that together constitute multiple copies of the entire genome of the spotted owl. The researchers have isolated individual microsatellite clones from the library and have determined their DNA sequence.

The sequence data allowed the researchers to build short DNA primers for the microsatellite locations. Together with a method known as the polymerase chain reaction (PCR), these primers enable the researchers to analyze the microsatellite repeats in feather DNA. Differences that are found at the microsatellite locations within feather DNA will be used to create a database of genetic variations for the spotted owl. When the database is complete, the team will be able to identify every individual bird within the population. Some of the questions that will be answered in the study include how far the birds travel, how long they live, how successful they are at reproducing and whether they are site-specific.

A comparison of DNA from different populations will be useful in making management decisions if the number of one group begins to decline. Restocking decisions could depend on information about genetic similarities between healthy populations and one that is in crisis.

The genetic data also will help researchers assess the long-term effect, if any, that the Cerro Grande Fire will have on the spotted owl populations. After the fire was put out and the smoke cleared, researchers found that 90 percent of Los Alamos County's habitat for the Mexican spotted owl had been lost. Luckily, none of the nests being monitored by the team studying the owl's genetic characteristics were damaged. Nonetheless the fire did reduce the overall area that young owls can occupy as they become reproductively mature and set out to develop their own nesting territories. The ongoing project will help determine if this loss of habitat will result in any significant change in the population's level of genetic diversity.