Science Spotlight

The California Department of Fish and Wildlife (CDFW) has completed its 2018 waterfowl breeding population survey -- and it’s good news for hunters and birdwatchers alike, as the total waterfowl population in the state now tops out at over a half million, for the first time in six years.

Melanie Weaver, who oversees CDFW’s Waterfowl Program, said that duck populations responded positively to the wet winter conditions of 2017. “Given the good upland and wetland habitat conditions last year from excessive precipitation, we anticipated good production,” she said. “We are pleased to see that higher recruitment reflected in this year’s breeding population survey.”

The full Breeding Population Survey Report, which can be found on the CDFW website, indicates the 2018 breeding population of mallards increased from 198,392 in 2017 to 272,859 (an increase of 38 percent). Mallards are the most abundant waterfowl species in the state, followed by gadwall (102,637) and cinnamon teal (78,498).

Other ducks that increased in number include northern shovelers, wood ducks, redhead and canvasback. Overall, the total number of ducks increased from 396,529 to 549,180 (an increase of 39 percent).

A few duck species did decline, including American wigeon, northern pintail, lesser scaup, ring-necked duck, ruddy duck and common merganser. But Weaver gave two possible explanations for these dips. First, none of these species are considered “strong nesters” in California. They migrate through the state, but don’t breed here in high numbers. And second, the survey is designed for dabbling ducks, meaning that diving ducks (such as mergansers) are harder for biologists to detect.

The survey also included Canada geese, which dropped slightly in number, from 55,224 in 2017 to 54,851 this year. (Canada geese are detected and recorded throughout the survey; however, the number reported refers to the traditional nesting population in northeastern California.)

CDFW biologists and warden pilots have conducted this survey annually using fixed-wing aircraft since 1948. The population estimates are for those areas where the vast majority of waterfowl nesting occurs in California, including wetland and agricultural areas in northeastern California, throughout the Central Valley, the Suisun Marsh and some coastal valleys.

In 2018, the survey was flown April 24-28 in the Central Valley and May 9-10 in northeastern California. A few planned survey segments were cancelled due to weather conditions (fog in the Napa-Santa Rosa area, and high winds in a few planned transects in the northeastern part of the state). However, the crew was able to cover 97 percent of the planned survey transects.

The majority of California’s wintering duck population originates from breeding areas surveyed by the U.S. Fish and Wildlife Service (USFWS) in Alaska and Canada. Those survey results should be available in early August. CDFW survey information, along with similar data from other Pacific Flyway states, is used by the USFWS and the Pacific Flyway Council when setting hunting regulations for the Pacific Flyway states, including California.

CDFW Photo

###

Media Contacts:
Melanie Weaver, CDFW Wildlife Branch, (916) 445-3717
Kirsten Macintyre, CDFW Communications, (916) 322-8988
 

A dwindling population of a tiny owl in Southern California has a chance at a comeback, thanks to a collaborative effort by scientists from CDFW, the San Diego Zoo’s Institute for Conservation Research (ICR), Caltrans and the U.S. Fish and Wildlife Service.

The Western burrowing owl (Athene cunicularia hypugaea) is currently listed as a Species of Special Concern, and nongame scientists have long been concerned about their viability and survival. Breeding populations have especially declined in the central and southern coastal areas, due in large part to a combination of habitat loss and eradication of the ground squirrels that dig out the burrows where the owls make their nests. In San Diego County specifically, the once-widespread population has been reduced to a single breeding node in the Otay Mesa region, just north of the Mexico border.

Two groups in particular have been monitoring these owls carefully, in an effort to help. Biologists from Zoo’s ICR have spent seven years assessing owl population status and productivity, including assessing the feasibility and effectiveness of artificial burrows, refining techniques to help the ground squirrels thrive and disperse into new areas and developing a system of identifying potential new locations where the owls might thrive. Much of ICR’s owl research has been conducted at Brown Field, a small municipal airport near the border within the City of San Diego, and on an adjacent property owned by Caltrans.

Meanwhile, about 10 miles from the Brown Field study site, CDFW scientists have spent a decade working to create more suitable burrowing owl habitat at Rancho Jamul Ecological Reserve (RJER). Efforts there included installation of artificial burrows and mowing the tall grass to foster a low-growing grassland suitable for burrowing owls and ground squirrels. Despite their best efforts, CDFW scientists studying the Rancho Jamul site have experienced many years of disappointment -- although wintering owls have shown up every year, none have stayed and attempted to breed on the property. But conditions have been improving over the last four years, thanks to the implementation of a grazing program that reduced dense thatches of old grasses and expanded areas of open ground. As habitat changed at Rancho Jamul, CDFW scientists observed more squirrel burrows, and the conditions seemed just about right for the owls.

This spring, an approved development project at Brown Field began to take shape – and it became evident that the timing for an owl translocation project was ripe at last. Thanks to efforts by Caltrans, which incorporated burrowing owl habitat restoration as part of their mitigation effort for a nearby highway, CDFW staff believed the owl population to be strong enough to support a translocation effort. Also the spring season, just prior to egg-laying, is likely the optimum time to move the animals. After looking at many options, scientists decided to try to move five pairs of breeding owls to RJER in the hopes that they would establish a new population and thrive.

The full conservation team – which included CDFW, the U.S. Fish and Wildlife Service, the City of San Diego, Metro Air Park, Schaefer Ecological Solutions and the San Diego Zoo – was on board and ready to move the owls. In March 2018, the team caught five pairs and moved them to hacking cages at RJER. The owls lived in the cages for about one month to give them time to acclimate to their new surroundings. By the time the cages were removed, each female had laid at least one egg in the artificial burrow chamber.

CDFW Environmental Scientist Dave Mayer has worked on this project for years and is anxious to see efforts at RJER finally pay off. The presence of the eggs, he said, was thrilling to see. “More owls, and at diverse locations, is what it will take to conserve this species in San Diego County. This first step was a long time coming, but I have all my fingers crossed that it’s going to work.”

This successful multi-agency partnership will continue long past the actual translocation day. Scientists banded the owls and fitted some with radio transmitters. ICR staff will monitor the owls themselves, while CDFW staff will monitor the grassland and the grazing program, and perform inspections and repairs of the artificial burrows twice a year. After five years, CDFW will perform regular monitoring of the owls, the habitat and associated grazing practices, and the general status of the ground squirrel population.

Mayer is proud of the work achieved so far in this unusual project. “We built a better mousetrap, with the Zoo’s help,” he says. 

General information about California’s bird species of special concern can be found on the CDFW website, along with the species account (PDF) for the burrowing owl and information about Rancho Jamul Ecological Reserve.

The San Diego Zoo has also issued a news release with more details about the burrowing owl translocation project.

All photos © San Diego Zoo Global, all rights reserved

# # #

The California Department of Fish and Wildlife (CDFW) has completed its annual waterfowl breeding population survey.

Mallards, gadwall and cinnamon teal comprised 54 percent of the ducks observed, down 30 percent from last year. The number of mallards decreased from 263,774 to 198,392 (a decrease of 25 percent) and total ducks decreased from 417,791 to 396,529 (a decrease of five percent).

The most notable decrease occurred in the Sacramento Valley area, where mallards were estimated at a record low of 31,000 (73 percent below the long-term average).

Given the abundant precipitation, one might expect the numbers to be higher. In some parts of the state, it did indeed increase available habitat (uplands and ponds). But in many areas, last winter’s heavy rains largely resulted in deep, fast-flowing water, which is not ideal for dabbling ducks. Other reasons for low duck observations could include winter flooding of nesting habitat that normally remains dry, the late-season flooding of the rice fields in the Sacramento Valley and the conversion of rice fields and pastures to tree crops.

CDFW biologists and warden pilots have conducted this annual survey using fixed-wing aircraft since 1948. This year’s survey was conducted from April 3 through May 4 in the Central Valley, and May 9-10 in northeastern California. The population estimates are for the surveyed areas only, which include the majority of the suitable duck nesting habitat in the state. Surveyed areas include wetland and agricultural areas in northeastern California, throughout the Central Valley, the Suisun Marsh and some coastal valleys.

The full Breeding Population Survey Report can be found at www.wildlife.ca.gov/conservation/birds/waterfowl.

The majority of California’s wintering duck population originates from breeding areas surveyed by the U.S. Fish and Wildlife Service (USFWS) in Alaska and Canada. Those survey results should be available in early August. CDFW survey information, along with similar data from other Pacific Flyway states, is used by the USFWS and the Pacific Flyway Council when setting hunting regulations for the Pacific Flyway states, including California.

A tiny, endangered mammal is the subject of an extraordinary conservation effort near the communities of Shoshone and Tecopa in Inyo County.

The Amargosa vole is unique to the Mojave Desert, and today, scientists estimate there are only about 500 remaining in the wild. Though the Amargosa vole is rarely seen by humans, biologists recognize that it is a key link in the native food chain. Predators, including raptors and water birds, share the desert marshes where they live, and the extinction of the Amargosa vole would have a ripple effect on these and many other species as well.

For a year, a scientific team consisting of CDFW, UC Davis and US Geological Survey biologists have conducted intensive research into the life cycle of this little vole. The team visited every marsh that potentially could be inhabited by voles – they mapped the marshes, assessed habitat quality, and determined whether or not voles were present. In a subset of larger marshes the team conducted more detailed assessments of water inflow-outflow, soil moisture and vegetation, and captured voles to estimate local population numbers, assess the health of the voles and take samples for disease and genetics studies. In addition to the hands-on study in the desert, they also studied satellite data to track the amount of vegetation and water in the area over a period of time. A grim picture emerged of a habitat range in decline, due in large part to climate change and human modification.

Some of the findings included:

• Total available habitat for the voles decreased 37 percent between 2012 and 2015.
• Over decades, global climate change has caused a gradual decrease in water in this region. California’s recent drought has exacerbated the problem.
• Of the more than 80 marshes that were documented at the beginning of the study, about 60 have degraded and/or dried up. Those that remain are almost all too small to sustain vole populations. Just as pandas eat only bamboo, the Amargosa vole survives solely on bulrush, a plant that grows in desert marshes.
• Another important finding was that 80 percent of the individual voles found and tracked during the study were adults. This indicates low birth rates and survival rates for juveniles – more barriers to the species’ recovery.

Scientists believe that the network of springs and marshes in the vole’s natural range has been so extensively modified by humans that the vole’s future existence will depend almost entirely on whether humans continue to supply water where and when needed. They found evidence to support this, as an intensive restoration effort at one of the largest marshes showed signs of successfully supporting and sustaining voles.

The report authors identified several specific measures that could be taken to increase vole habitat and improve their chances of survival – including reconfiguring water inflow and outflow, changing elevations and planting vegetation that would enhance existing marshes and/or better connect adjacent marshes.

This study is part of a larger long-term effort to secure a future for the Amargosa vole and the unique marsh ecosystems it depends upon in the Mojave Desert. In late 2014 vole numbers became so low that scientists initiated a captive breeding program at the UC Davis School of Veterinary Medicine to reduce the risk of extinction. Today more than 100 voles are in the captive colony at UC Davis – providing a potential source of animals for release into restored habitats, and an important insurance population to prevent extinction.

Photos by Don Preisler/UC Davis School of Veterinary Medicine