Incubation behavior reflects how birds balance the thermal needs of developing embryos against their own requirements for self-maintenance, with consequences for nest survival and hatching success. This behavior is expected to vary among species based on evolutionary history and life-history strategies. We used motion-activated trail cameras to compare incubation-recess behavior of 2 cavity-nesting ducks, a perching duck (Aix sponsa [Wood Duck]) and a sea duck (Lophodytes cucullatus [Hooded Merganser]), both using nest boxes in Louisiana and Mississippi. Despite differences in life history and foraging ecology between perching-and sea-duck guilds, the species exhibited broadly similar nest attentiveness. Wood Ducks averaged 2.55 +/- 0.58 recesses per day, and Hooded Mergansers averaged 2.49 +/- 1.12 recesses per day, and daily incubation constancy was similar (87.1% vs. 86.9%). In contrast, recess timing differed consistently between species. Wood Ducks initiated morning recesses earlier (06:54 +/- 0.58 h) than Hooded Mergansers (09:01 +/- 0.76 h), whereas Hooded Mergansers tended to recess earlier in the afternoon (15:18 +/- 0.40 h) than Wood Ducks (16:19 +/- 1.12 h). Within species, Wood Duck morning recess duration decreased with increasing clutch size (-7.9 +/- 2.9 min/egg), while Hooded Merganser morning recess duration declined across incubation (-5.6 +/- 1.9 min/ day). Overall, the clearest divergence between species occurred in recess timing rather than the intensity of incubation behavior.

Many waterfowl species and closely related congeners are shared across the Holarctic, and are culturally and economically important in both North America and Europe. Accordingly, both continents have developed science and management frameworks in an attempt to establish evidence-based conservation practices for this guild of birds. However, the 2 continents have approached this shared challenge from surprisingly different angles, wherein there is much to be learned from each other via increased collaboration across the Pond. In the United States and Canada, there is relatively strong alignment of conservation values, and the role of hunters in the science and management of waterfowl has a deeply embedded cultural and financial legacy. This differs markedly from Europe, where there is much more discordance among countries and constituents, resulting in regulatory policies that are uneven and generally rely on the precautionary principle. Here, we describe key differences in the waterfowl science and management enterprises in North American and Europe, and highlight key avenues for increased collaboration for mutual benefit.

Targeted monitoring by trained professionals has been the standard to inform evidence-based regulatory and conservation planning decisions for migratory waterfowl and other wildlife in North America. As inferential expectations derived from professional surveys grow and funding wanes, decision-makers are turning toward citizen science as supplemental or alternative data sources. However, external validation of citizen science data, in cooperation with experts, is recommended before their use in management decisions. We compiled data from professional surveys across 7 U.S. states within the Upper Mississippi / Great Lakes Joint Venture (JV) for 16 species of waterfowl (ducks, geese, and swans) to compare with and potentially validate temporal trends in weekly relative abundance predictions (i.e., migration curves) by eBird citizen science data. We demonstrated that eBird weekly relative abundance produced similar migration curves to those derived from professional surveys for most species. Concordance between migration curves for uncommon or vagrant species was less reliable, especially at the county level. However, at spatial scales more relevant for regulatory or conservation planning decisions (e.g., state or JV scale), correlation between eBird and professionally derived migration curves increased to adequate levels of concordance for most species (p ≥ 0.70). We concluded that eBird weekly relative abundance is a suitable supplement to professional surveys to generate migration curves for waterfowl conservation planning during the nonbreeding season. Additionally, states and JVs that lack monitoring at appropriate temporal frequency may consider using eBird relative abundance to derive migration chronologies for priority species that are well-distributed throughout their region. Broadly, we encourage continued external validation of citizen science data—which requires close partnership between researchers and decision-makers—for its wise use in management decisions.

Understanding how waterfowl respond to habitat restoration and management activities is crucial for evaluating and refining conservation delivery programs. However, site-specific waterfowl monitoring is challenging, especially in heavily forested systems such as the Mississippi Alluvial Valley (MAV)-a primary wintering region for waterfowl in North America. We hypothesized that using uncrewed aerial vehicles (UAVs) coupled with deep learning-based methods for object detection would provide an efficient and effective means for surveying non-breeding waterfowl on difficult-to-access restored wetland sites. Accordingly, during the winters of 2021 and 2022, we surveyed wetland restoration easements in the MAV using a UAV equipped with a dual thermal-RGB high-resolution sensor to collect 2360 digital images of non-breeding waterfowl. We then developed, optimized, and trained a RetinaNet object detection model with a ResNet-50 backbone to locate and identify seven species of waterfowl drakes, waterfowl hens, and one species of waterbird in the UAV imagery. The final model achieved an average precision and average recall of 88.1% (class ranges from 68.8 to 99.6%) and 89.0% (class ranges from 70.0 to 100%), respectively, at an intersection-over-union of 0.5. This study successfully surveys non-breeding waterfowl in structurally complex and difficult-to-access habitats using UAV and, furthermore, provides a functional, open-source, deep learning-based object detection framework (DuckNet) for automated detection of waterfowl in UAV imagery. DuckNet provides a user-friendly interface for running inference on custom images using the model developed here and, additionally, allows users to fine-tune the model on custom datasets to expand the number of species classes the model can detect. This framework provides managers with an efficient and cost-effective means to count waterfowl on project sites, thereby improving their capacity to evaluate waterfowl response to wetland restoration efforts.

In the early 1900s, wood duck Aix sponsa populations experienced severe declines due to unregulated hunting and habitat destruction. Federal protection under the Migratory Bird Treaty Act of 1918 and the implementation of nest box programs facilitated their recovery such that sport harvest resumed in 1941. In 2008, the bag limit for wood ducks during the general duck season increased from two to three daily, a change projected to increase the harvest rates. However, estimating harvest and survival rates of adult females remains challenging due to the difficultly of capturing them during preseason banding operations. We analyzed data from 2001-2014 from box-nesting female wood ducks in Louisiana using a live-dead model to estimate survival and calculate harvest rates. Our results indicate the bag limit increase had minimal impact on the survival and harvest rates of box-nesting females. The mean annual survival rate was 68%, with no changes after the increase in bag limit in 2008. Harvest rates also remained consistent across the study period, averaging 3%. Our findings suggest the increase in bag limit has not adversely affected survival of box-nesting wood ducks in Louisiana, allowing for additional hunting opportunities without compromising conservation goals for adult female wood ducks in the state.

Coronaviruses (CoVs) were first described in poultry in the early 1930s and formally recognized as pathogens of both animal and human populations in the late 1960s. They are now considered among the most abundant viral families in the world. Though their distribution and diversity remain understudied in wild animals, representatives from 13 orders of wild birds worldwide have tested positive for CoVs of the gamma and delta genera over the last 25 years. Many of these wild bird species are in the orders Charadriiformes (shorebirds and their relatives) and Anseriformes (waterfowl including ducks, geese, and swans). Waterfowl are particularly concerning as potential reservoirs for CoVs because they are globally distributed; often congregate in large, mixed-species flocks; and may exist in close proximity to humans and domesticated animals. This review describes the history and current knowledge of CoVs in birds, provides an updated list of global detections of CoVs in 124 species of wild birds as reported in the peer-reviewed literature since 2000, and highlights topics for future research that would help elucidate the role of waterfowl in CoV transmission. Our review reiterates the need for continuous surveillance to detect and monitor CoVs across all bird species and for standardization in data reporting and analysis of both negative and positive results. Such information is critical to understand the potential role of free-ranging birds in the maintenance, evolution, and transmission of the virus. Further, we believe that research on the potential impacts of coronavirus infections and coinfections on avian demographics, especially reproduction in waterfowl, is warranted given known consequences in domestic poultry.

Traditional methods for estimating juvenile survival in wildlife populations often rely on marking and tracking individual young. However, traditional methods can introduce bias into survival estimates via the capture or handling process and are logistically challenging to implement. Alternatively, researchers studying avian and mammalian species that provide parental care can mark and monitor adults to estimate survival probability of the unmarked offspring. We implemented a field sampling approach using unoccupied aerial vehicles (UAVs, i.e., drones) to estimate detection probabilities and pre‐fledging survival of blue‐winged teal ( Spatula discors ) by marking and resighting adult females with broods ( n = 27). We used a combination of 2 methods to detect marked females, drone‐based VHF radiotelemetry and multispectral imagery, to estimate brood detection and apparent survival using Cormack‐Jolly‐Seber models. We compared between the VHF drone and the camera drone to investigate the ability of the VHF drone to locate marked females and thermal cameras to detect broods. Detections using the camera drone were informed by prior location cues from the VHF drone, meaning that detections were not independent but instead relied on the cues provided by the VHF drone. We monitored marked females and their unmarked broods weekly during the summer of 2023 in Saskatchewan, Canada. Of marked females, 9 suffered complete brood loss (33%), 4 had unknown fates (15%), 14 had at least one duckling survive to 35 days (52%), and we observed that 120 of 230 ducklings survived. Detection probability for sampling with the VHF drone remained constant over time (mean = 0.920), whereas detection probability using the camera drone increased with each sampling occasion (mean = 0.756). Weekly brood survival probability increased with brood age and were similar between survey methods (VHF: mean = 0.907; camera: mean = 0.898). Capitalizing on the interdependence of unmarked juveniles and marked adults, and drone‐based methodology, our approach allowed us to effectively and efficiently estimate juvenile survival for waterfowl. Our approach is applicable to a range of other species as well, where providing more precise and efficient field sampling methods for monitoring vital rates and population dynamics can enhance ecological understanding and resultant management practices.

Nest site selection is a discrete and often repeated choice, and individuals should select nest sites that maximize reproductive success and thus increase fitness. Mottled Ducks (Anas fulvigula) are a non-migratory species that inhabits the Gulf Coast of the United States year-round and therefore have the ability to constantly evaluate habitat to make well-informed nest site choices compared to migratory species. Mottled Duck populations have declined over the last decade and a better understanding of nest site selection and its relationship to nest survival is a top research priority. We deployed GPS transmitters on 148 females across three breeding seasons to evaluate nest site habitat selection and nest survival. We observed 30 nest attempts and found females selected sites in diverse landscapes, but Mottled Ducks preferred old fields and pasture relative to other habitats. High vegetation density surrounding the nest bowl had a positive influence on nest survival. We found that females were more likely to renest when the initial nest failure occurred earlier in the incubation period. Our results emphasize the importance of preserving tall, dense vegetation in upland habitats. Additionally we recommend that prescribed burns are timed to ensure adequate vegetative cover for Mottled Ducks by the onset of nesting in March.

In the southeastern United States, wood ducks (Aix sponsa) have historically experienced interspecific brood parasitism (IBP) primarily from hooded mergansers (Lophodytes cucullatus), but the recent northward expansion of black-bellied whistling-ducks (Dendrocygna autumnalis) has added a new complexity to these interactions. We monitored nest boxes in Louisiana to evaluate the influence IBP had on wood duck daily nest survival rate (after, DSR) and duckling recruitment. We monitored 1,295 wood duck nests from 2020-2023 and found 112 (8.7%) were parasitized by hooded mergansers and 148 (11.5%) by whistling-ducks. Parasitic egg-laying by hooded mergansers lowered wood duck DSR, while DSR for nests parasitized by whistling-ducks was comparable to clutches containing only wood duck eggs. We considered the wood duck capture histories of 2,465 marked female ducklings and 540 banded adult females to estimate a duckling recruitment probability for the entire study period. We recaptured 50 ducklings as adults; 6 (12.0%) hatched from clutches parasitized by hooded mergansers, 1 (2.0%) from a clutch parasitized by a whistling-duck, and 43 (86.0%) from clutches containing only wood duck eggs. The duckling recruitment probability was 0.039 (95% credible interval = 0.028, 0.051). Nest initiation date had a negative effect on recruitment, wherein most recruits hatched from nests initiated earlier in the season. Given only ~9% of wood duck nests contained hooded merganser eggs, we conclude IBP writ large had no detrimental effect on DSR at a population level. The lower DSR of clutches parasitized by hooded mergansers is potentially linked to a high abundance of early-season parasites that produce "dump nests" and these clutches are often abandoned without being incubated. Despite ongoing parasitism by hooded mergansers and the range expansion of whistling-ducks, wood duck productivity in Louisiana appears to be minimally affected by interspecific brood parasitism.

Black-bellied Whistling-Ducks (Dendrocygna autumnalis; BBWD) are rapidly expanding northward into the core range of the eastern Wood Duck (Aix sponsa; WODU), yet little is known about BBWD nesting ecology. Typical field methods to study cavity-nesting waterfowl (i.e., weekly nest monitoring) preclude a full understanding of important breeding information, including nest prospecting and parasitic egg laying. To address this, we used subcutaneous passive integrated transponder (PIT) tags embedded in adults and PIT tag readers mounted on nest boxes with the objective to (1) identify individuals that used nest boxes but were not physically captured on a nest, (2) quantify box visitation, and (3) quantify BBWD pair and WODU hen behaviors during the prospecting, laying, and incubation periods. We deployed RFID readers on 40 nest boxes from March-December 2022 in Louisiana with the potential to detect BBWD and WODU marked with PIT tags in 2020-2022. We detected 48 (BBWD n = 26, WODU n = 22) adults of both species via RFID readers, and 33% (n = 16) of individuals (50% of BBWD, n = 12; 14% of WODU, n = 3) were never otherwise recaptured in 2022, meaning that traditional field methods for cavity-nesting waterfowl fail to document a substantial number of birds potentially contributing to the population via parasitism. We also used Bayesian generalized linear models to determine that both species visited a similar number of "new" (< 1 year old) and "old" (> 1 year old) nest boxes (beta = 0.66, CI = -0.30, 1.64). However, BBWD preferentially visited (and subsequently nested in) old boxes at a significantly higher rate than WODU (beta = 1.32, CI = 0.97, 1.66). Due to the generalist nature and rapid expansion of BBWD, an apparent aversion to newly installed boxes was unexpected, especially since there were several successful WODU nests in the new boxes before BBWD began nesting in 2022. Our study is one of the first to evaluate BBWD nesting behaviors within the core WODU breeding range, and the first to use nest box-mounted PIT tag readers to observe BBWD behavior.

Abstract Louisiana surveys waterfowl hunters every 5 years to assess hunter effort, harvest success, demographics, and preferences for proposed regulations and management practices. The 2020 Survey of Louisiana Waterfowl Hunters addressed hunter satisfaction patterns, hunter perceptions on waterfowl migration, associations of field experiences to satisfaction, associations among distribution waves, the efficacy of sample coverage by an email survey, and allowed comparison with hunter satisfaction with surveys in 2005, 2010, and 2015. We distributed a 31‐question survey by email to 73,554 Louisiana waterfowl hunters following the 2019–2020 season. We received 13,483 total responses, of which 8,218 were usable (licensed respondents actively hunting waterfowl during the 2019–2020 season), resulting in a qualified response rate of 12.0%. We compared qualified respondents to the overall population of Harvest Information Program registrants (169,891) and found no significant differences for age class, geographic distribution, and license type. Our results indicated that surveys should be distributed in 3 waves, as the number of days hunted would be overestimated by 7% (mean of 15 days [95% confidence interval = 14.7–15.7] compared to a mean of 14 days [95% confidence interval = 13.7–14.4]) by a single survey. Hunters' satisfaction was independent of which geographic zone they hunted, whether they were members of conservation organizations, or how many waterfowl were seen. Our results also indicated that the probability of greater hunter satisfaction was increased by 98% as the number of waterfowl harvested surpassed 57, by 68% for respondents reporting that their actual harvest exceeded expected harvest by at least one bird, and by 61% for respondents reporting that their actual days hunted exceeded expected days hunted by at least one day.

Artificial nesting structures have been used to aid the recovery and maintenance of certain avian populations such as the wood duck (Aix sponsa). The success of nest boxes for wood ducks relies on excluding common nest predators such as raccoons (Procyon lotor) and rat snakes (Pantherophis spp.) via the use of predator guards; however, woodpeckers cannot be excluded. Red-bellied woodpeckers (Melanerpes carolinus) are foraging gen-eralists and have been anecdotally observed preying on wood duck eggs where documenting predation events is difficult to accomplish through traditional nest box monitoring. Here, we used custom-modified trail cameras to document egg depredations and foraging events by red-bellied woodpeckers and the removal of damaged eggs by wood ducks during the laying and incubation periods. We captured 35,686 videos and documented 1173 different events consisting of 608 (51.8%) videos of red-bellied woodpeckers and 565 (48.2%) of wood ducks. We determined 38 (30.6%) eggs were depredated during the laying period and 14 (11.3%) during incubation. Wood ducks removed 23 (60.5%) eggs depredated during the laying period and 13 (92.9%) depredated during incu-bation. We found no difference in the daily number of times red-bellied woodpeckers visited boxes with nests in the laying or incubation period (t = - 0.967, df = 14.699, P = 0.349). Red-bellied woodpeckers depredated 1.0 ?? 0.2 eggs during each event and returned to forage on previously depredated eggs 5.3 ?? 4.4 times each day spending 2.1 ?? 1.1 min during each return. Our results suggest that red-bellied woodpeckers forage on eggs when nests are unguarded, and they have previously been under-recognized in the literature as predators of wood duck eggs. Future nest box programs should consider the impact red-bellied woodpeckers have on wood duck egg loss and nest survival.

The Prairie Pothole Region (PPR) is globally important for breeding waterfowl but has been altered via wetland drainage and grassland conversion to accommodate agricultural land use. Thus, understanding the ecology of waterfowl in these highly modified landscapes is essential for their conservation. Brood occurrence is the cumulative outcome of key life-history events including pair formation and territory establishment, nest success, and early brood survival. We applied new technological advances in brood surveying methods to understand brood use of wetlands and how land use and wetland-specific factors influenced brood use of 413 wetlands in crop-dominated landscapes in the PPR of Iowa, Minnesota, North Dakota, and South Dakota, USA, during summers of 2018-2020. Dynamic occupancy models combining information from 2 visits throughout the year revealed no difference among the 4 states or between private and public lands, resulting in a region-wide annual wetland occupancy estimate of 0.41 (95% credible interval [CrI] = 0.26, 0.58). We assessed aquatic invertebrate forage availability, wetland and upland vegetation communities, and various water chemistry metrics in a subset (n = 225) of these wetlands to evaluate how landscape and wetland-specific factors influenced occupancy. The amount of grassland surrounding wetlands was the only variable to influence occupancy at a landscape scale, while wetland size, invertebrates, fish, and vegetation communities influenced occupancy at finer scales. Closer scrutiny of wetland area revealed occupancy was greater in small wetlands after controlling for total wetland area. Our results indicate the greatest constraint on brood occupancy across crop-dominated landscapes of the PPR in the United States was the occurrence of semipermanent wetlands suitable for brood rearing. Other factors, such as wetland vegetation or surrounding land use, had minor intervening influences on duck brood use and ducks were distributed invariant of wetland ownership or broad spatial processes occurring among states. These results demonstrated wetland conservation and restoration strategies are likely to yield gains in annual duck broods across this vast, altered, and highly modified landscape.

The dynamics of wintering waterfowl populations at the landscape scale are the result of complex interactions of environmental, behavioral and energetic drivers. Agent-based models provide a method to directly link these factors in a spatially explicit framework and allow the emergence of patterns from the aggregation of individual agent actions. We adapted the Spatially-explicit Waterbird Agent-based Model Program (SWAMP), originally developed for waterfowl in central California, to simulate a basin-scale population of mallards (A. platyrhynchos) wintering in the Mississippi Alluvial Valley over a four-month period (November-February). Simulated agents move within the landscape, foraging on areas made available based on a probabilistic inundation status, and converting food resources to endogenous energy. The model uses a high-resolution map of eastern Arkansas waterfowl habitats and incorporates a hierarchical habitat selection system that enables mallards to relocate at increasing scales in response to changing food availability. We validated the performance of modeled mallard body condition and behavioral metrics under a range of environmental conditions against expected outcomes derived from empirical data and found that the simulation produced realistic representations of changes in flight distances, energy expenditure, lipid storage, and foraging habitat use in response to depleting food resources over time. We discuss the model's applicability as a tool to quantify waterfowl response to a range of environmental conditions and to evaluate scenarios of landscape composition and configuration in the context of waterfowl population management.

Adult survival is a key driver of waterfowl population growth and is subject to temporal and spatial variation. Mottled ducks (Anas fulvigula) are native to the Gulf Coast and peninsular Florida, USA, and have suffered population declines over the past decade, especially in Texas and Louisiana, USA. Although the cause of this decline is not well understood, previous research concluded variation in survival contributed to nearly a third of variation in the species' population growth rate. We used global positioning system-groupe special mobile (GPS-GSM) transmitters to study temporal and spatial variation in survival of adult female western Gulf Coast mottled ducks in southwestern Louisiana, 2017-2020. We evaluated weekly survival models parameterized with combinations of hunted and non-hunted periods, biological seasons, and landcover types that were used by mottled ducks. There were 3 competitive survival models, and all contained 4 parameters that parsed the annual cycle into the non-hunted period, first part of the general waterfowl season, and second part of the waterfowl season, and included the proportion of GPS locations in agricultural lands. Weekly survival was 0.979 during the first part of the general waterfowl hunting season, and 0.996 during the second part of the general waterfowl season. Daily survival rate increased with an increasing proportion of locations logged in agricultural lands. Annual survival rates were similar to other waterfowl that are not experiencing population declines, which suggests survival is not limiting population growth of mottled ducks along the western Gulf Coast. Managers should ensure the availability of refuge areas where hunting is prohibited during the first part of the general waterfowl season, when mottled ducks are at an increased risk of mortality, in addition to the targeted conservation of agricultural lands that provide cover and forage.

The Mallard (Anas platyrhynchos) duck is a ubiquitous and socio-economically important game bird in North America. Despite their generally abundant midcontinent population, Mallards in eastern North America are declining, which may be partially explained by extensive hybridization with human-released domestically derived game-farm Mallards. We investigated the genetic composition of Mallards in the middle and lower Mississippi flyway, key wintering regions for the species. We found that nearly 30% of wild Mallards carried mitochondrial (mtDNA) haplotypes derived from domestic Mallards present in North America, indicating that the individuals had female game-farm Mallard lineage in their past; however, nuclear results identified only 4% of the same sample set as putative hybrids. Recovering 30% of samples with Old World (OW) A mtDNA haplotypes is concordant with general trends across the Mississippi flyway and this percentage was stable across Mallards we sampled a decade apart. The capture and perpetuation of OW A mtDNA haplotypes are likely due to female breeding structure, whereas reversal of the nuclear signal back to wild ancestry is due to sequential backcrossing and lower and/or declining admixture with game-farm Mallards. Future studies of wild ancestry of Mississippi flyway Mallards will benefit from coupling molecular and spatial technology across flyways, seasons, and years to search for potential transitions of Mallard populations with different genetic ancestry, and whether the genetic ancestry is somehow linked to an individual's natal and subsequent breeding location. Lay Summary center dot Mallard ducks are common worldwide but are declining in the Atlantic flyway of eastern North America, a decline that may be influenced by widespread hybridization between genetically wild Mallards and domestic game-farm birds that are released for hunting. center dot We used hunter-harvested birds to investigate possible westward expansion and hybridization rates in the lower Mississippi flyway. center dot Despite recovering 30% of samples possessing game-farm Mallard-derived mitochondrial DNA, only 4% were identified as hybrids across thousands of nuclear loci. center dot Prevalence of game-farm Mallard-derived mitochondrial haplotypes were consistent in Mallards sampled a decade apart, suggesting mitochondrial introgression can be captured and persist within lineages far longer than nuclear DNA. center dot Whereas the prevalence of wild x game-farm Mallard hybrids remains significantly less in the lower Mississippi relative to the Atlantic flyway, continued genetic monitoring and development of management strategies to abate future hybridization will be required.

Black-bellied Whistling-Ducks (Dendrocygna autumnalis; Whistling-Duck) are undergoing a rapid range expansion northward and now breed throughout the Southeastern United States. As a facultative cavity-nesting species, they have the potential to compete with Wood Ducks (Aix sponsa) and Hooded Mergansers (Lophodytes cucullatus) for nest sites. Little is known about Whistling-Duck breeding biology, and estimates of clutch characteristics and rates of conspecific and interspecific brood parasitism (CBP and IBP, respectively) are lacking. We monitored Whistling-Duck nests in Louisiana to describe nesting chronology, clutch size of parasitized and unparasitized (normal) nests, and hatchability (i.e., the portion of eggs that hatched) for clutches of different sizes and types. We monitored a total of 558 nest boxes between 2020–2021 and determined the presence of brood parasitism for 231 Whistling-Duck nests. CBP was detected in 73 (31.6%) nests, and IBP was observed in 51 (22.1%) nests parasitized by Wood Ducks, two (0.9%) nests parasitized by Hooded Mergansers, and one nest contained eggs from all three species. Normal clutches were smaller (15.4 ± 4.4 eggs) than CBP clutches (26.1 ± 8.8 eggs) and mixed clutches (22.2 ± 5.3 eggs; clutches containing Wood Duck or Hooded Merganser eggs; all pairwise P < 0.0001). However, within clutch repeatability, estimates for egg morphology data (i.e., length, width, and mass) were low (< 0.40) for normal clutches, suggesting CBP went undetected. Of 180 fated nests used to determine hatchability, 66 (36.7%) were successful, 49 (27.2%) were abandoned, 64 (35.6%) were depredated, and one (0.6%) was nonviable. Considering successful nests, hatchability was high for all clutch size bins ranging from 67.4% (41–45 eggs) to 81.6% (11–15 eggs). Our study is the first to document Whistling-Ducks successfully hatching mixed-species broods, and such high productivity could be contributing to Whistling-Duck range expansion.

Geolocators are small devices that record and store time-stamped light levels that researchers typically use to approximate the latitude and longitude of small birds across the annual cycle. However, when geolocators are affixed to leg bands of larger-bodied birds, nest incubation by females interrupts the daily pattern of light and darkness. Thus, geolocators can provide information on nesting propensity, nest success, and renesting intensity; these demographic parameters are both difficult to measure unobtrusively and are critically important in determining population dynamics of birds, especially ducks. Here, we deployed 240 geolocators on mottled ducks Anas fulvigula in Louisiana and Texas in 2018-2019 to evaluate their utility in providing nesting data. During July 2018-January 2022, we recovered 16 geolocators from hunter-harvested birds, and learned of 6 other unreported recoveries, yielding a realized recovery rate of 7.1% (9.1% unrealized). Three of the recovered units provided breeding-season data. Two of these clearly indicated a single nest initiation in the early spring of 2019, and one of the units also logged an attempt in spring of 2020. Ducks incubated all three nests for approximately a month, suggesting that they all successfully hatched. The final geolocator logged five putative nest attempts over the course of 2 y. In 2019, both attempts were unsuccessful (incubated < 10 d). In 2020, we documented three attempts spanning 20 February-10 June, all of which appeared to have failed. For all failed attempts, the hen left the nest at dusk or overnight and did not return, which is suggestive of mammalian predation. Geolocators successfully provided information on breeding-season activities of mottled ducks, and we documented renesting rates following nest depredation. However, we achieved a smaller sample size than anticipated (three usable returns), resulting in an effective cost of $11,800 per usable return. Where possible in other species, capturing birds immediately prior to the breeding season, and improvements to geolocator attachment have the potential to improve recovery rates and increase cost effectiveness of the technique.Copyright: All material appearing in the Journal of Fish and Wildlife Management is in the public domain and may be reproduced or copied without permission unless specifically noted with the copyright symbol &. Citation of the source, as above, is