Essay, part of a special feature on Partners in Flight International Science Committee: Migratory Bird Conservation Tools and Applications

INTRODUCTION

Loss of biodiversity remains among the greatest challenges we face, accelerated by intensifying land use, resource exploitation, and habitat loss, and exacerbated by global climate change. Steep declines of bird populations and resulting species endangerment are global in scope and symptomatic of disrupted ecological processes and erosion of overall environmental health (Lees et al. 2022). In the U.S. and Canada alone, nearly 3 billion birds have been lost since 1970, with over 300 species declining across every major habitat and biome (Rosenberg et al. 2019). Understanding and addressing widespread declines and threats to migratory species presents huge challenges for science-based conservation, as species distributions span regional and national jurisdictions and occupy vast geographies across annual cycles.

Recognition of bird population declines across North America is not new. Over 60 years ago, disappearing birds inspired the title of Rachel Carson’s Silent Spring (Carson 1962). In response, Chandler Robbins created the North American Breeding Bird Survey (BBS) to track and document changes in bird populations. Robbins et al. (1989) published the first comprehensive analysis of BBS trends, sounding the alarm for declines of Neotropical migrants. The scientific community rallied to better understand the extent and nature of these declines. Hagan and Johnston (1992) synthesized the then-rudimentary knowledge of migratory bird biology, and Where have all the birds gone? (Terborgh 1990) further alerted the conservation-minded public to the disproportionate population loss of Canadian, U.S., and Mexican long-distance migrants and the challenges of abating threats to these hemispheric species.

In 1990, in response to growing scientific and public concern, a consortium of over 150 government agencies, non-governmental organizations, academic institutions, and industry leaders from primarily the U.S., Canada, and Mexico developed a continentally scaled bird conservation strategy that initiated working groups for monitoring, management, research, education, regional partnerships, and international cooperation (NFWF 1990). This broad and diverse consortium soon coalesced as Partners in Flight—Aves de las Americas—Partenaires d’Envol and Compañeros en Vuelo (hereafter PIF). A foundation of science and partnership was central to PIF from the outset (Stangel and Eno 1992). As working groups and initiatives continue to evolve, PIF and its International Science Committee (hereafter PIF Science) continue their commitment to use the best available, collaborative, and co-produced^[1] science to underpin shared conservation goals and actions across the full life cycle of declining birds.

In this paper, we (1) describe PIF’s collaborative science-based approach to conserving bird populations, (2) present an overview of PIF’s science tools and products with example bird conservation outcomes, and (3) offer a vision for the future of PIF Science to unite a diverse bird conservation community to recover bird populations and “keep common birds common.” Additional papers in this Avian Conservation and Ecology special feature more extensively highlight flagship PIF tools and projects, including the Avian Conservation Assessment Database (ACAD), Population Estimates Database (PED), an assessment of PIF population trend objectives, and new full annual cycle conservation planning tools that PIF Science has released over the last decade.

PIF Science approach

Prior to 1990, bird conservation in the U.S. and Canada was limited largely to endangered species recovery, gamebird management, and local-scale projects aimed at benefiting species considered popular or locally rare. To address widespread declines across hundreds of migratory nongame species, however, PIF developed an approach that was (1) proactive, addressing needs of species before they required federal listing; (2) voluntary and highly collaborative, drawing on the strengths of the diverse PIF network; and (3) grounded in the principles of conservation biology and expert knowledge of North American^[2] birds. PIF’s model at that time was the North American Waterfowl Management Plan, an ambitious strategy for recovering waterfowl populations in the U.S. and Canada to sustain waterfowl populations and habitat (USFWS 1986). Could this approach be replicated and expanded to conserve > 700 non-game bird species across North America?

PIF’s multi-species, science-based approach is built on a foundation of scientific knowledge about birds and the threats they face and is guided by four strategic goals (Rich et al. 2004, Alexander 2011, Rosenberg et al. 2016):

• Maintain healthy bird populations in healthy habitats and ecosystems;
• Keep species from becoming threatened or endangered through proactive measures and science-based planning;
• Practice full life-cycle conservation of migratory birds;
• Promote the value of birds as indicators of environmental health and human quality of life.

PIF’s planning approach follows a stepwise, collaborative path to pinpoint greatest conservation need, target science and conservation, and assess progress across the full life cycle of birds. These steps include:

• Assessing a species’ relative conservation vulnerability;
• Identifying focal species and habitats most in need of science and/or conservation action and determining relevant scales for conservation action;
• Setting numerical population objectives for species of continental and regional importance;
• Setting habitat-based conservation objectives and identifying relevant conservation actions;
• Identifying suites of focal species representative of desired habitat conditions;
• Working with partners to implement strategies for meeting species and habitat objectives at continental and regional scales;
• Evaluating conservation outcomes using habitat measures, focal species response, and priority species population trends;
• Using an adaptive management approach in revising conservation priorities, objectives, and actions as new data and evaluation results become available.

PIF’s approach resulted in bird conservation plans for 38 physiographic areas and 12 states within the continental U.S. (Pashley et al. 2000) and formed the basis for the PIF North American Landbird Conservation Plan (Rich et al. 2004, Rosenberg et al. 2016) and Saving Our Shared Birds: PIF Tri-National Vision for Landbird Conservation covering Canada, the U.S., and Mexico (Berlanga et al. 2010). Many other bird conservation planning efforts at multiple scales adopted elements of PIF Science plans, including State Wildlife Action Plans for all 50 U.S. States,^[3] Canadian Bird Conservation Region Strategies,^[4] Migratory Bird Joint Venture plans, and most recently a set of Conservation Business Plans for regions and high-concern species.^[5]

To address the challenge of focusing science needs and conservation actions on suites of vulnerable species and their habitats while prioritizing limited financial and logistical resources, PIF Science developed a standardized process to assess the conservation vulnerability of species at multiple geographic scales (Hunter et al. 1993, Carter et al. 2000). This data-driven, rules-based assessment has continued to evolve, incorporating key refinements following an American Ornithologists’ Union Conservation Committee review (Beissinger et al. 2000), harmonizing concepts and methods across Canada and the U.S. (Dunn 1997, Dunn et al. 1999), expanding scope to add about 450 Mexican landbird species (Berlanga et al. 2010), and, finally, becoming today’s all-bird ACAD, which provides vulnerability scores and associated metadata for over 1600 species in 10 countries from Canada south through Central America (PIF 2024). The ACAD remains a key PIF Science tool and go-to bird conservation resource that offers scientifically defensible and comparable information on species status and promotes coordinated conservation across spatial scales, political jurisdictions, and organizational boundaries.

To address the challenge of setting numerical population objectives for conservation, PIF pioneered a methodology for estimating population sizes of U.S. and Canadian landbirds using existing monitoring data sources and provided these estimates at multiple scales in the PED (Rosenberg and Blancher 2005, Blancher et al. 2007, PIF 2020). As with the species vulnerability assessment, methods for population estimation have been critiqued (Matsuoka et al. 2012, Sólymos et al. 2020) and refined (Stanton et al. 2019) over time, and a major effort is currently underway to use new modeling frameworks and data sources to improve estimates for all U.S. and Canadian birds (Edwards et al. 2023; Gahbauer et al. unpublished manuscript).

PIF has long recognized the critical importance of bird monitoring to identify and track species of greatest concern and, as conservation plans began to inform implementation and management, to test assumptions and measure the effectiveness of conservation actions on the ground. Standardized survey methods (Ralph et al. 1993), monitoring needs assessments (Downes et al. 2000), and coordinated monitoring programs (Bart and Ralph 2005) were developed within PIF to streamline data collection for widespread access and use (Dunn et al. 2005a). PIF also provided feedback to improve the conservation value of long-term surveys (Dunn et al. 2005b, U.S. NABCI 2007, Rosenberg et al. 2017). Today, the Avian Knowledge Network (Iliff et al. 2009) provides a secure repository of bird monitoring data and offers processes for discovery and large-scale analyses.

Throughout the development of its science approach, PIF rallied the ornithological community at a series of international symposia, workshops, and conferences resulting in 384 published papers (Finch and Stangel 1993, Bonney et al. 2000, Ralph and Rich 2005, Rich et al. 2009) that introduced new concepts, tested assumptions, and synthesized a growing body of collective knowledge about bird conservation. These collaborative opportunities led to numerous targeted working groups, funding initiatives, conservation planning tools, and products that have guided the bird conservation community for more than 35 years. PIF was among the first to integrate concepts of conservation biology for nongame birds into traditional state and federal wildlife conservation agencies and organizations, e.g., providing spatially explicit conservation targets for area-sensitive bird species (Brown et al. 2000, Mueller et al. 2000, Pashley and Warhurst 2000, Baxter 2005). Concepts of conservation design were further developed to assist with planning at ecoregional scales (e.g., Altman 2005), to address the threats to migratory birds across their annual cycles (Will et al. 2005), and to encourage management-relevant science delivery and decision support (Alexander et al. 2009). Population declines highlighted by PIF also inspired the formation of numerous species-focused working groups (e.g., Golden-winged Warbler [Vermivora chrysoptera], Cerulean Warbler [Setophaga cerulea], Bicknell’s Thrush [Catharus bicknelli], western hummingbirds) that focused attention on species-specific threats, knowledge gaps, limiting factors, collaborative conservation actions, and, ultimately and hopefully, recovery of the species (Boves 2011, Colorado et al. 2012, Dawson et al. 2012, Skolnik et al. 2012, Boves et al. 2013a, 2013b, McFarland et al. 2013, Wood et al. 2013, Ralston et al. 2015, Bennett et al. 2016, Rosenberg et al. 2016, Aldinger et al. 2017, Lloyd and McFarland 2017, Roth et al. 2019, Gillespie et al. 2020, Woodie et al. 2023, Ernest et al. 2024).

From its inception through today, PIF spotlights the need for full annual cycle research and bird conservation programs while advancing public and institutional communication about the plight of migratory birds. Internationally focused publications like Saving Our Shared Birds (Berlanga et al. 2010) brought together ornithologists from Canada, the U.S., and Mexico to highlight declining migratory birds shared across North America together with at-risk tropical resident species, their common threats, and strategies to work effectively across borders. PIF science products continue to encourage partners primarily focused on breeding-range conservation efforts to visualize species connections to equally important non-breeding habitats (Blancher et al. 2006, Stewart et al. 2023) and take action (Sánchez-Nivicela and Montenegro-Pazmiño 2022, González et al. 2023). These products guide conservation investments targeting nonbreeding habitats (e.g., Southern Wings program for U.S. states, U.S. Neotropical Migratory Bird Conservation Act, Canada’s Nature Fund) and encourage collaborations among international partners for declining bird species shared across the Western hemisphere.

PIF’s lasting impact on bird conservation

For 35 years, PIF has been a catalyst for shifting the landscape of traditional wildlife conservation from endangered and game bird species management to the coordinated stewardship of all bird species. The lasting impact of PIF Science begins with the large body of conservation plans, databases, technical publications, and other tools that are ubiquitous across the bird conservation community today (Table 1, Appendix 1). For example, the ACAD and PED databases have far-reaching applications, serving as indispensable decision support tools for conservation planning and action at multiple scales; species assessments and population objectives are utilized across U.S. and Canadian federal agencies, U.S. state agencies, migratory bird habitat Joint Ventures, and numerous conservation organizations. The PIF Science databases also serve as the science foundation for eight U.S. State of the Birds reports since 2009 that highlight critical bird conservation concerns for both legislators and the conservation-minded public (e.g., see NABCI 2022). These reports were followed by the State of North America’s Birds (NABCI 2016) and the State of Canada’s Birds (NABCI Canada 2012, 2019).

PIF’s impact on reimagining the limited paradigm of the 1980s extends far beyond its science products, however, even if the open-door, collaborative, and voluntary nature of PIF’s organization makes direct quantification difficult. For example, the focused attention and concern for declining songbirds from PIF and other conservation organizations led to renewed commitment to the Migratory Bird Treaty Act (Clinton 2001) and authorization of the Neotropical Migratory Bird Conservation Act; growth of migratory bird programs and funding initiatives within federal agencies in the U.S., Canada, and Mexico; creation of State Wildlife Action Plans and the associated State Wildlife Grant Program in the U.S.; expansion of the migratory bird Joint Ventures to cover all birds and terrestrial habitats; and a proliferation of new bird conservation and research organizations (cf. Table 1, Appendix 1). As a case study, we track the impact of PIF Science on the conservation of the Cerulean Warbler (Fig. 1).

Billions of birds lost: need for more targeted science and action

After more than three decades of focused conservation attention and research, however, many bird species continue to exhibit precipitous declines. In 2019, inspired by a question posed at the July 2017 PIF Science meeting, a comprehensive analysis to quantify net bird loss drew on population size estimates and trends in PIF Science’s ACAD and PED databases and reported a loss of 2.9 billion breeding birds since 1970 in the U.S. and Canada alone, with over 300 species, including habitat generalists, declining across every major habitat and biome (Rosenberg et al. 2019). Migratory bird species continue to exhibit the steepest declines and largest losses, especially long-distance migrants spending the non-breeding season in South America (40% loss in population since 1970). This sobering result led to a reevaluation of conservation priorities and a call for redoubling our efforts to recover and sustain healthy bird populations (NABCI 2021). The “three billion birds lost” message reverberated with unprecedented media coverage and public attention and inspired parallel studies across Europe (Burns et al. 2021, Gregory et al. 2023), showing that avifaunal loss of similar magnitude was a global phenomenon. As part of a coordinated response to these findings, long-tenured ornithologists from PIF Science formed the Road to Recovery (R2R) initiative to shine a spotlight on over 100 bird species in the U.S. and Canada whose precipitous declines had reached a tipping point.^[6] Attention to short-term declines and metrics of urgency were subsequently incorporated into ACAD and reflected in the categorization of species included on the PIF Watch List (Panjabi et al. unpublished manuscript). Acknowledging that we still lack essential data on precise limiting factors and causes for decline for many species, R2R promotes a targeted approach to recovering Tipping Point Species via expanded support of Species Working Groups, integration of biological and social science, and co-production (sensu Beier et al. 2017) of sustainable solutions. Species Working Groups (SWGs) focus research and collaboration on declining species with a focus on better understanding where and when in the annual cycle limiting factors are impacting populations. Importantly, a focus on SWGs is not exclusive to vital programmatic work to protect ecosystems, however, failure to address limiting factors for the most steeply declining species is likely to result in further loss.

A vision and strategies for the future of PIF Science

PIF Science remains committed to providing science tools to halt the loss of species abundance and to focus research and conservation actions to prevent additional species from slipping through the conservation cracks. To achieve greater impact, face new urgent challenges, and ensure continuity of expertise and purpose, we envision a future focused on the points below:

Better aligning bird conservation objectives among agencies, conservation organizations, ornithological societies, and global goals for biodiversity, restoration, and area protection in order to eliminate gaps, reduce redundancy, leverage capacities, and maximize impact:

• PIF efforts include consistently convening bird-conservation groups (e.g., NABCI, R2R, Joint Ventures) for workshops and roundtables at international and academic conferences to ensure communication and collaboration across the bird-conservation community. More must be done to increase efficiency and continue to define niche roles in this community to avoid redundancy.

Increasing engagement, capacity, and resources across the hemisphere to empower all voices in ornithology, including Latin American and Indigenous leadership, expertise, and priorities:

• Sustaining commitment to international co-production that explicitly recognizes the knowledge and interests of a wide variety of partners at project inception and continues to bridge the pivotal gap between knowledge and conservation action and delivery (i.e., Conservation Investment Strategies [Sánchez-Nivicela and Montenegro-Pazmiño 2022, González et al. 2023], Making Connections for Bird Conservation [Stewart et al. 2023]);
• PIF’s Western Working Group and PIF Science’s new Migration Ecology Subcommittee provide simultaneous Spanish-English translation at all meetings. Translation of existing PIF plans into Spanish has also been initiated. This model should be applied to all PIF working groups and committees to continue building a welcoming community for participation and collaboration across the hemisphere;
• PIF continues its foundational, collaborative science and partnership to drive conservation investment and solutions in initiatives like the Association of Fish and Wildlife Agencies’ Southern Wings program (https://southern-wings.fishwildlife.org/) for U.S. state agency investment in migratory bird conservation.

Leveraging novel and growing technologies (e.g., Motus Wildlife Tracking System), data sources (e.g., eBird), and modeling methods to improve existing assessment tools and address the most critical knowledge gaps:

• PIF Science’s flagship databases (ACAD and PED) will continue evolving, led by open committees of subject matter experts and regional avian ecologists to integrate the most robust datasets and experiment with new methodology to provide consistently updated and reliable bird-population estimates and threat scores for the bird conservation community;
• There is continued commitment to knowledge-sharing and community building on migratory bird ecology and tracking methods via PIF Science’s new Migration Ecology Subcommittee.

Ensuring all avian scientific data are preserved in public-facing, easily accessible databases prioritizing the effective transfer of science-based information to communities of conservation actors who can implement strategies that benefit birds and their habitats (Alexander 2011, Iliff et al. 2009):

• PIF Science has ensured open, easy access to its databases (ACAD and PED) and will continue to do so into the future;
• PIF provides a network that works to leverage collaboration and overcome agency and organizational silos to promote innovation (i.e., Avian Knowledge Network^[7]) and conservation tools (i.e., Neotropical Flyways Project,^[8] Audubon Migration Explorer^[9]) that maintain accessible avian data.

Highlighting continued integration of social and biological science to fill critical knowledge gaps, including the importance of understanding human dimensions and behaviors that lead to declines in bird populations, but can also contribute to recovery:

• PIF will continue to elevate and grow its partnership with Road to Recovery, NABCI, and Joint Ventures in their dedication to social science and its vital role in recovery efforts for declining bird species.

As we implement these strategies, we need voices of future conservation leaders, including students and young professionals across a spectrum of disciplines and geographies. New voices are emerging from a landscape of urgency that requires deep understanding and commitment to address a new set of conservation challenges. They are ready. PIF Science’s new Migration Ecology Subcommittee, established in 2024, deliberately empowered next-generation leadership in its co-chairs. This approach of recruiting younger leadership must be emulated if we are to ensure the success and longevity of conservation groups. Passing the torch to a new generation of leaders inspires PIF Science with optimism for the future of bird conservation. We hope that this optimistic vision can serve as a model for collaborative science-based conservation of birds and other taxa in other regions of the world.

Science serves as a grounding factor in conservation and brings us together. Now more than ever, bird conservation groups must unite with one voice to find efficiency, synergy, and strengthen our niches to better conserve rapidly declining bird populations. For its part, PIF Science provides an open, welcoming organizational framework and knowledge base to support conservation planning and implementation across the bird conservation community as it always has and will continue to do.

__________

^[1] Defined as “collaboration among managers, scientists, and other stakeholders, who, after identifying specific decisions to be informed by science, jointly define the scope and context of the problem, research questions, methods, and outputs, make scientific inferences, and develop strategies for the appropriate use of science” (Beier et al. 2017).
^[2] North America includes countries from Canada through Panama and the Caribbean.
^[3] https://www.fishwildlife.org/afwa-informs/state-wildlife-action-plans
^[4] https://www.canada.ca/en/environment-climate-change/services/migratory-bird-conservation/regions-strategies.html
^[5] https://nabci-us.org/bird-conservation-community/bird-partnerships/conservation-business-plans/
^[6] Tipping Point species exhibit high vulnerability to extinction and severe population declines as described in tiers at https://r2rbirds.org/tipping-point-species.
^[7] https://avianknowledge.net/
^[8] https://neotropicalflyways.com/
^[9] https://explorer.audubon.org/

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