The Recommendations
Recommended Updates to Duck Population Objectives
1. Adjust the Traditional Survey Area Time Series
The Plan Committee will adjust the period used for Traditional Survey Area objectives by (1) choosing 1974 instead of 1955 as the starting year, and (2) adding data from 2015–2023 to the data used in 2014, thus making 1974–2023 the basis for long-term averages (LTAs).
A careful analysis of the changing survey design and protocols during the earliest years of the WBPHS TSA indicates that the 1974–2023 time series is more appropriate for determining LTA objectives (2024 Update Technical Report). Survey effort increased significantly from 1955 to 1974, transect locations changed and stratum boundaries were redrawn over existing transects. Another significant protocol change occurred in 1974, when observers stopped recording unidentified ducks, leading to an increase in the number of identified birds of some species. Lack of detailed documentation for some of these changes limits our ability to accommodate the early data using model-based analytical approaches. Therefore, the 1974–2023 time series represents a consistent period of survey effort and allocation, with better documentation of survey design changes. It is also long enough (50 years) to represent a wide range of habitat conditions and waterfowl populations. Using the later start date results in a minor change in NAWMP LTA objectives for most species, and those species that were below goal levels in 2014 remain below the new recommended goal levels (Appendix C; also see the 2024 Update Technical Report).
2. Expand Eastern Survey Area Objectives
Mallards and American Black Ducks
For mallards and American black ducks in the Eastern Survey Area, NAWMP objectives will include estimates from all of eastern North America, an expanded region beyond the eastern core survey area that includes state and provincial surveys, and an extended period 1998–2023 for calculating the LTA and 80th percentile objectives.
American Black Duck Population Estimation
For American black ducks a 1:1 breeding pair correction for population estimation is recommended, as it is currently being used in the American black duck adaptive harvest management framework. For other duck species in the east, it is recommended that population objectives include ducks from the entire WBPHS Eastern Survey Area (2024 Update Technical Report).
The ESA expansion will produce higher NAWMP population objectives than the 2014 Addendum and 2018 Update, but it represents a more comprehensive estimate of the true population size in the eastern continent (Appendix C; also see the 2024 Update Technical Report). In addition, these revised eastern objectives will inform more Habitat Joint Venture planning areas compared to previous coverage.
3. Review How Population Objectives Are Formulated
The Plan Committee, prior to the next Update, will ask the NAWMP Science Support Team (NSST) to review how population objectives are formulated, specifically to (1) consider the utility of the current scale of NAWMP objectives for conservation planning, (2) assess the capacity of current monitoring frameworks to provide information needed by the Joint Ventures for effective objective setting, and identify gaps that should be filled; (3) undertake the analytical work, if necessary, to derive new population objectives that are useful at local geographies, but that can be integrated to the continental scale. Two specific questions are: What data might best be used to inform habitat conservation planning for western-breeding mallards and other ducks (see Appendix D)? What is the potential utility of incorporating state survey estimates for conservation planning by mid-continent Joint Ventures?
The first duck population objectives were anchored to the mid-continent TSA and, after 2014, to both the TSA and the ESA of the annual WBPHS. However, growth in the number of operational breeding waterfowl surveys and advances in analytical techniques have provided a more comprehensive accounting of continental waterfowl populations. Harvest management frameworks increasingly use more population information (e.g., provincial and state surveys for western and mid-continent mallards) to focus harvest strategies at relevant population scales. Using these same more inclusive data sources for NAWMP population objectives might improve alignment with planning regions and close the gap between the spatial bases for habitat and harvest management objectives, improving the coherence of these management systems. This effort will ensure that NAWMP population objectives remain relevant and useful for setting habitat objectives and assessing conservation progress.
4. Support Flexible Joint Venture Planning
The decision about whether or when to plan for average conditions (LTA population objectives) or exceptional circumstances (80th percentile), and whether to collaborate with adjacent Joint Ventures to plan for and accommodate desired populations under either planning scenario, is best left to the experienced planners in each Joint Venture with guidance from the NSST. Joint Ventures managing nonbreeding and migration stopover habitat should employ methods of Fleming et al. (2019) to step down preferred objectives to their local geographies.
Joint Ventures (JVs) should have the flexibility to employ dual continental objectives and methods in order to step down, or adapt, these objectives to relevant spatial scales. A primary purpose of dual objectives, first articulated in the 2014 Addendum, was to encourage conservation planners to recognize the variation inherent in ecosystems when envisioning the landscape conditions needed to support LTA waterfowl populations, and to acknowledge that occasional exceptional conditions are needed to offset inevitable periods of poor conditions. Thus, population or habitat objectives are not static values to be achieved annually, but rather are the desired long-term product of the variation inherent in ecosystems plus JV management actions. Based on diverse experiences of the Habitat Joint Ventures since 2014, application of dual planning targets will make sense for some JVs but not for all. Likewise, JVs that include nonbreeding and migratory stopover habitat require flexibility to interpret continental objectives in terms of their unique geographies as well as the waterfowl life cycle period they support. Accordingly, the NSST is encouraged to examine the formulation of these joint objectives and to help with cross-JV planning to ensure that a suitable level of habitat redundancy occurs among JVs to support expected bird populations during both population highs and lows. The NSST has refined and endorsed a consistent framework (Fleming et al. 2019) for stepping down NAWMP population objectives to regional scales, allowing JVs to customize objectives to their specific planning needs.
5. Assess Population Estimation Methods and Data Sources
A critical examination of how NAWMP population objectives are formulated is needed to ensure that they are based on the best available data and modern analytical techniques and that they provide relevant and useful benchmarks for setting habitat objectives and gauging conservation success. We encourage collaboration among federal technical staff, the NSST and other researchers to resolve uncertainties and differences in estimates produced from different data sources and techniques.
From the beginning, the NAWMP has been distinguished by its commitment to evidence-based management, built on a solid foundation of scientific monitoring. Annual monitoring of waterfowl breeding populations by the WBPHS and other breeding surveys has provided valuable long-term information on population abundance, distribution and variation and should be sustained. These surveys also provide vital benchmarks for measuring NAWMP management success at the continental and regional levels.
Since the 2018 Update, Mexico has restarted monitoring programs to document the distribution, abundance and species composition of waterfowl. This represents the first national, systematic monitoring carried out by Mexican technical staff, fostering the interaction of the government with civil society. The new monitoring data will allow managers to assess conservation status of waterfowl, identify critical habitats, develop management policies and strategies, monitor environmental impacts and threats, foster education and awareness platforms, and support scientific research.
Increasingly, waterfowl managers are using other biological data and analytical techniques that provide additional information about populations. Band recoveries and harvest estimates have long been used to estimate survival or account for mortality in population models, and Bayesian estimation frameworks are now commonly used in integrated population and mark-recapture models that combine these data streams (Alisauskas et al. 2013). Some NAWMP population objectives are based on these model outputs already (e.g., Eastern Survey Area estimates; some goose population objectives).
Evidence from recent banding analyses using Lincoln estimators has challenged some of the assumptions of other population surveys, leading to potentially divergent conclusions about continental waterfowl population trends. Given the importance of these population data to planning and evaluating success in the NAWMP, we recommend that the waterfowl management community undertake a critical assessment of waterfowl population estimation, including an evaluation of assumptions and potential biases of different methods and data sources. This assessment should involve collaboration among federal technical staff, the NSST and other researchers.
6. Formalize a 10-Year Review Cycle
The Plan Committee will formalize review of population objectives every 10 years, consistent with the recommendation in the 2018 Update. This schedule is compatible with the frequency with which most Joint Ventures update their conservation plans and would allow them to incorporate any changes during their routine update processes.
