FACTORS REGULATING WOOD DUCKS IN LAHONTAN VALLEY, NEVADA

• Sponsoring Institution: State Agricultural Experiment Station
• Project Status: COMPLETE
• Funding Source: STATE
• Reporting Frequency: Annual
• Accession No.: 0218207
• Project Start Date: Mar 1, 2009
• Project End Date: Aug 31, 2012
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF NEVADA
(N/A)
RENO,NV 89557

Performing Department
Natural Resources & Environmental Sciences

Non Technical Summary
Little is known about Wood Ducks in Nevada. They are a lightly harvested species with current harvest estimates averaging 400 birds per year within the state of Nevada. Wood Ducks are an easy species to study and monitor due to less time involved in nest searching due to their behavior of nesting in cavities, especially man-made nesting structures. The habitat Wood Ducks use in and around Fallon, Nevada, the limitation of such habitats in the area, and relative isolation from other Wood Duck populations make this study unique in that the potential for an intense capture-recapture-recovery project is high. This allows for an intense study design which has not been accomplished with other duck populations and provides an optimal situation for exploring many hypotheses which have been difficult to address in ducks.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
315	3240	1060	100%

Knowledge Area
315 - Animal Welfare/Well-Being and Protection;

Subject Of Investigation
3240 - Duck and goose, live animal;

Field Of Science
1060 - Biology (whole systems);

Keywords

wood ducks

survival rate

harvest rate

reproductive success

Goals / Objectives
The primary goal of this project is to understand survival, harvest rate, reproductive success, and recruitment of the wood duck. The standard methodology to study these questions uses a combination of marking individuals with unique tags (e.g. standard and coded legbands and webtags), subsequently encountering these individuals (recaptures, resightings, and hunter reports), and monitoring nesting effort.

Project Methods
We are conducting this study along the lower Carson River in Churchill County, Nevada. Nevada Waterfowl Association has installed 340 nesting boxes to date and have collected nesting data form these boxes annually since 2003. Monitoring of nesting boxes begins approximately the 3rd week of March when the first nests are initiated. We visit all nests boxes weekly through the middle of July at which time all nests have hatched. We record information such as: 1) what species may be using the box (Wood Ducks, American Kestrels, European Starlings, Western Screech Owls, and Northern Flickers), 2) clutch size, 3) Wood Duck egg measurements, 4) laying order, 5) incubation stage by candling eggs, and 6) identity of the hen. We label each egg and collect measures of length and width. We also replace the nesting material (wood shavings) as necessary. Nevada Waterfowl Association has conducted an intense banding program on Wood Ducks in the Fallon area since 2003. We begin baiting sites following the close of duck season, usually late January and continue baiting our sites through nesting and brood rearing and conclude baiting sites ten days before duck season opens. Rocket nets and air-cannons have been used in areas where landowners have been feeding birds for some time and also where we have placed bait to attract them. Lastly, we are also able to capture nesting hens and the ducklings from these nests. At all instances in which we capture Wood Ducks, all individuals are marked with unique markers. Webtags are typically used for marking ducklings in the nest box prior to departure from the nest site. All Wood Ducks that are large enough to hold standard aluminum leg bands are fitted with such markers. All Wood Ducks which are large enough to hold bands are also banded on the opposite leg with a 1cm tall yellow PVC band with two black engraved characters. Nasal saddles were placed on all nesting hens and a sample of SY and ASY males and females captured in the time period following nesting. We began using coded tarsal bands and nasal saddles to attempt to be able to identify individuals without having to physically capture them. By using spotting scopes at loafing or feeding sites, we can read these markers at distances up to 200 meters. We attempt to assign all captured or harvested individuals to age and gender and also record several measurements. We collect the following morphological measures: diagonal tarsus, culmen, total head, 9th primary, wing chord, body, and weight. Hunters encounter our marked birds when hunting Wood Ducks. All bands are engraved with the 1-800-327-BAND toll-free band number to facilitate reporting harvest of a banded bird to the USGS Bird Banding Laboratory. Beginning in 2008, we provided a photograph and a request to report harvest of webtagged Wood Ducks in NDOW's waterfowl hunting pamphlet. By following the fates of individually marked Wood Ducks, we will be able to provide estimates of survival controlling for age, sex, year, and season. In combination with estimates of fecundity, we will be able to produce a population model for Wood Ducks nesting in Nevada which will be useful for managers.

Progress 03/01/09 to 08/31/12

Outputs
OUTPUTS: For additional information, please contact Kelley Stewart at 775-784-4314 or [e-mail] PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
For additional information, please contact Kelley Stewart at 775-784-4314 or [e-mail]

Publications

• No publications reported this period

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: We estimated daily nest survival rates for wood ducks (Aix sponsa) breeding in artificial nest boxes in Nevada from 2004-2010 to assess effects of nest characteristics and variation among individual females in nest success. We also assessed the impacts of visiting nests or capturing females on daily nest survival. The random effect of individual female accounted for 7% of variation in nest survival, but only 15% of this individual process variation was accounted for by individual process covariates. We detected a significant interaction between the effect of capturing a female and nest age. Capturing a female on the first day of egg laying reduced daily nest survival from 99.8% to 98.2% whereas capturing a female on the 42nd day of the nest period was associated with an increase in daily nest survival from 98.2% to 99.6%. Nest success did not vary among years and averaged 66%. Our analyses provide evidence that observer-related nest abandonment by females is at least partially compensatory to other forms of nest failure during the first half of the nesting period. We also provide evidence of substantial variation among individual females in the probability their nest hatched, independent of nest sites and female nutritional status. We found substantial annual variation in adult female survival (43-63%). Mortality during the breeding season contributed substantially more to annual variation in survival than mortality during the non-breeding season; variation in survival during the breeding season accounted for 54% of total annual variation in survival while variation in survival during the non-breeding season accounted for only 1% of the variation in annual survival, despite a five-fold increase in harvest rate. Clutch size in first nests of the season and whether the nest was parasitized or not, were positively related to breeding season survival. We view these results as preliminary because other measures of quality such as body size, condition, or laying date were not strongly related to survival. We suggest that variation in λ is driven by adult survival, because nest success in this population does not vary. Our analyses provide evidence that substantial variation in annual female survival is explained by variation during the breeding season, and imply that mechanisms other than predation on incubating females can account for significant variation in survival of breeding waterfowl. PARTICIPANTS: Nevada Department of Wildlife Nevada Waterfowl Association Dept. of Natural Resources and Environmental Science TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
This study is the first of wood ducks in Nevada and will provide key data to be used for management.

Publications

• No publications reported this period

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: This project continues substantial outreach to the public in the Lahontan Valley, and substantil interaction with Nevada Department of Wildlife and Nevada Waterfowl Association. PARTICIPANTS: Nevada Department of Wildlife U. S. Fish and Wildlife Service Nevada Waterfwol Association James S. Sedinger PI Christipher Nicolai, co-PI Steve Olson, gradutate student TARGET AUDIENCES: Nevada Department of Wildlife U. S. Fish and Wildlife Service Nevada Waterfwol Association Public PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
We continued to catch wood ducks at extremely high rates this year from January 23 to current. We used rockets or air cannons to deploy a large net over baited areas. Six-hundred eighty four new USFWS bands have been put on this year. We also recaptured 825 wood ducks this year. Wood duck ducklings too small to hold standard bands were marked with webtags. Thirty-six ducklings were caught and tagged in this manner. Aside from physically capturing wood ducks, we were also able to re-sight 654 wood ducks at feeding sites and other opportunistic areas along the Carson River and irrigation ditches. Re-sights afford us the opportunity to know an individual is still alive without capturing and handling, which can lead to increased stress. We found 106 wood duck nests among the 425 artificial nesting structures we have built and dispersed along the Carson River. Three-hundred ninety nine ducklings were hatched out of 1234 eggs laid in these nests. Of these, I managed to tag 391 ducklings on their day of hatch, just before exodus of the nests. Research is focused on nesting ecology and reproductive correlates of female wood duck survival. In the next few months, we will be examining variables such as age, body condition, laying date, clutch size, and brood parasitism to see if they affect nest success. Besides providing information on the health of breeding wood ducks in Nevada, the estimates of nest success should lay the ground work for more interesting questions such as the short- and long-term effects of successfully hatching a brood, brood size, or brood parasitism on future female survival. These analyses will also be conducted within the next couple months and will eventually be published in a peer-reviewed scientific journal. Another analysis to be conducted soon is the effect of body condition on annual, seasonal, and monthly survival. The effect of winter body condition on breeding probability will be examined as well. Most banded waterfowl in North America will never pass through a restricted migratory funnel as many Pacific flyway wood ducks do, and therefore will never be re-encountered by the original bander. Because of our high trapping efforts around Fallon, Nevada, we have a 60-70 percent chance of encountering (recapture, re-sight, or hunter recovery) a banded wood duck throughout the year. The first step in a body condition analysis is to determine the most important body measurements and to calculate a composite variable that captures the most variance among individual wood ducks, called the first principal component. I recently carried out this step with 2283 unique wood ducks in four age and sex categories. Of the six body measurements analyzed, the first principal component was composed of the ninth primary length and wing chord measurements in all four age and sex categories. This is important because most wood duck investigators currently only measure culmen and tarsus, and we have statistically shown these measurements do not capture as much variance as the ninth and wing measurements.

Publications

• No publications reported this period

Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: Study in progress, no outputs yet. PARTICIPANTS: Chad August, gradaute student Chris Nicolai, Contract biologist Nevada Dept. Wildlife Craig Mortimore, Waterfwol Biologist, Nevada Dept. Wildlife TARGET AUDIENCES: Nevada Department of Fish and Game U.S. Fish and Wildlife Service PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Meadows and riparian areas in Northeast Nevada were surveyed for nesting cranes beginning in April 2009. A majority of the nest searching was done by searching on foot, but in addition we searched for nesting cranes with a variety of techniques including scanning using spotting scope and binoculars for nesting cranes, helicopter and airplane surveys, monitoring cranes for changing of incubation responsibilities, and ATV searching. A total of 61 nests were discovered in Northeast Nevada during summer 2009. Eleven of the nests found were already inactive (previously hatched or failed). Fifty active nests were monitored, of which 17 produced at least one colt (34% Apparent Nest Success). To determine colt survival, a 5-gram VHF radio transmitter was attached to the back of 51 colts using prong-and-suture. Colts were monitored approximately twice weekly. When colts reached three weeks of age, radio transmitters were removed and attached to auxiliary markers to be placed above the left tibiotarsus and a federal aluminum band was added above the right tibiotarsus.. Thirty colts were banded with auxiliary markers and federal aluminum bands. Of colts for which we determined fate, 12 colts survived to fledging and 15 colts succumbed to mortality (n=27). During fall pre-migration staging in August and September, adult cranes were banded on Ruby Lake NWR by rocket netting over a rye field baited with corn. During four shots, we were successful in capturing nine adult cranes. Eight of the cranes were banded using a USFWS aluminum band and a PVC auxiliary marker with a two-digit blue alpha-numeric code (one of the cranes was previously banded).

Publications

• No publications reported this period