Traditionally, conservation measures for endangered species have been applied based on land use and water quality changes. As recent as 2021, Lambertucci and Speziale (2021) introduced the concept of aerial habitat and aeroconservation. These authors proposed to include aspects of the airspace, extending from the land or water surface to the upper limit of the troposphere, in conservation, biodiversity and managements assessments (Lambertucci et al. 2015). Migratory species, such as Ruddy-headed goose, use airspace to travel between breeding and wintering grounds every year. Therefore, the identification and impacts occurring in this newly defined habitat might be crucial for the survival of these species. To the best of our knowledge, this study is the first to identify potential high-risk areas situated along the flyway of the Ruddy-headed geese based on satellite tracking data.
During autumn, important areas during migration pathways were mainly located in the south of Buenos Aires province. These areas in the Pampas region were categorized by Pedrana et al. (2014) as highly suitable for all sheldgeese species and are characterized by low elevation, high mean productivity and proximity to streams, lakes and/or ponds. Similarly, Pedrana et al. (2020) found that stopover sites of Ruddy-headed goose were also located in southern Buenos Aires province and that they mostly used areas far away from urban areas and mainly characterized by a low elevation terrain interspersed with streams and lakes. In Argentina, Martin et al. (1986) and Blanco et al. (2003) also described this association between sheldgeese and productive grounds and proximity to waterbodies, which may indicate the distribution of higher-quality foraging grounds and their strict dependence on water in their roosting sites. These relationships have been described for other geese species all around the world, which feed and rest in the proximity of waterbodies and wetlands that offer them not only a suitable place to feed, but also provide protection from potential predators (Carboneras 1992; Summers and Mc Adam 1993).
During spring migration, we found that important areas during migration pathways were located near the wintering grounds; the same was reported during autumn migration, and also near the breeding grounds in southern Patagonia. These areas were associated with low elevation, high mean productivity and proximity to waterbodies and streams. Most of these areas were categorized by Pedrana et al. (2011) in Patagonia and Pedrana et al. (2014) in the Pampas region as medium to high suitability areas for sheldgeese occurrence. Likewise, other studies found these associations of sheldgeese with wetlands and streams (Summers 1985; Martin et al. 1986; Summers and McAdam 1993). Although it is not clear that geese respond to topography per se, altitude might be correlated to certain landscape components or soil quality features (more productive environments typically occur in lowlands) which may have implications for goose habitat selection (Wisz et al. 2008).
In this study, a third of the overall area during spring and autumn migration categorized as high-density was located in the influence of the HV network, indicating a potential threat to Ruddy-headed geese. Rees et al. (2005) documented the same behaviour in Whooper Swans Cygnus c. cygnus. Some groups, such as seaducks are known to be particularly sensitive to disturbance from wind farms (Percival et al. 1997; Drewitt and Langston 2006), which could be the case of the Ruddy-headed goose.
The main negative effects of wind farms and HV networks may occur through disturbance, displacement during construction and maintenance as well as from improved road access as a result of the wind farm development, especially in areas where there was little human activity before these human infrastructures were built (Drewitt and Langston 2006, 2008, Bernardino et al. 2018, Marques et al. 2020). Given that the Ruddy-headed goose population is listed in Appendixes I and II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), more work is required to understand the extent to which the displacement of this species might translate into a significant population-level impact. It is important to mention that the satellite devices deployed in our study did not register the flight height. Future studies should take flight height into account to calculate the probability that birds might fly in the rotor-swept zone of wind turbines, a proxy for collision hazard (Péron et al. 2017).
Other adverse effects may include habitat loss/degradation, displacement from feeding areas, barrier effects, and disturbance (Powlesland 2009). For example, in Denmark, (Larsen and Madsen 2000) found that wintering Pink-footed geese Anser brachyrhynchus maintained a distance of about 100 m from single turbines or rows of turbines, and about 200 m from clusters of turbines. Similarly, Fox et al. (2006) highlighted the impact of the wind farm on reducing the local abundance of birds by displacing individuals to already occupied or otherwise unsuitable habitat.
Travelling over sea during autumn migration might decrease collision risk. Although, the new offshore wind farm building intentions that are increasing along the Patagonian Shelf, might cause a negative effect on Ruddy-headed goose migratory population (Palmer et al. 2017). In contrast, during spring migration, Ruddy-headed geese tracked flew over land and encountered at least two high-risk areas of conflict within terrestrial wind farms and HV networks: one located near the wintering grounds in Buenos Aires province and another one located in southern Patagonia, Santa Cruz province, Argentina. Large birds with poor manoeuvrability (such as swans and geese) are generally at higher risk of colliding with structures such as turbines and power-lines, which may directly impact on population sizes through additional mortality (Brown et al. 1992). Equally, these human-built structures may be perceived by birds as a barrier, demanding additional energy invested in flight to avoid the obstacle. Thus, potentially increasing energy expenditure can affect breeding success and survival (Madsen et al. 2014; Peschko et al. 2020). Even low numbers of anthropogenic induced fatalities of certain species can be additive to other causes of mortality and significantly reduce their population (Watson 2018). Moreover, turbines may disturb the foraging and breeding of waterfowl (Drewitt and Langston 2006) resulting in habitat loss (Larsen and Madsen 2000). Therefore, if we add collision risk to birds that are of conservation concern, such as the Ruddy-headed goose, a few deaths may have a large effect on a small remnant population.
Although we tracked almost 1% of the migrating population, our findings should be taken with caution. However, our results are essential for future management plans to prevent potential human-sheldgeese conflicts to escalate along their migration route. As mentioned before, Rudy-headed geese gather in large groups to start migration. So, even though we equipped only six individuals and tracked them for at least three consecutive migration cycles, we expect that more individuals were migrating together with the tracked ones. Complementary to tracking data, we believe it is important to perform ground surveys in breeding and wintering areas as well as in the stopovers. Another important finding associated to the deployment of satellite transmitters was the identification of four stopovers inside national parks boundaries (e.g. Monte León National Park, Bosque Petrification de Jaramillo National Park, Makenke Marine Interjurisdictional Park and The Patagonia Coastal Marine Interjurisdictional Austral) in agreement with Chebez et al. 1998. This information highlights the importance of protected areas along the Argentinean coastline. After these findings, a new agreement was signed with the National Park Administration to develop a monitoring program of these areas to record the areas used by the species during autumn and spring migration (Agreement EX-2020-73020515-APN-DGA#APNAC: INTA - APN Agreement Project for Ruddy-headed goose monitoring program). Furthermore, it is important to monitor protected areas as well as potential high-risk areas to record collision with wind turbines or HV lines. Further studies should include increasing numbers of sampled individuals and gather more information on migratory flyways or local flight paths, which would improve our understanding of wind farms and HV networks on Ruddy-headed geese. There is clear evidence that the probability of bird collisions with turbines and HV networks depends critically on species behaviour, especially flight behaviour, topographical factors and weather (Barrios and Rodríguez 2004; Drewitt and Langston 2008; Bernardino et al. 2018; Heuck et al. 2019; Marques et al. 2020). Therefore, further studies should focus on these factors.
During the development of the "Workshop on Good Environmental and Social Practices for the Wind Sector" held in Buenos Aires in March 2017, it was concluded that some birds’ species have high priority according to the risk of impact that wind farms can cause on them. These species were categorized according to their conservation status (IUCN Red List of Threatened Species and BirdLife International). In addition to the Ruddy-headed goose, other high-priority Patagonian species found on this list include the Andean condor, Vultur gryphus, the Hooded Grebe, Podiceps gallardoi, the Ashy-headed and Upland goose, the Chilean Flamingo, Phoenicopterus chilensis, the Magellanic plover, Pluvianellus socialis and the Red knot, Calidris canutus. Consequently, the potential hazard zones proposed on this study may also contribute to the conservation of other endangered species facing the same threats along the migration pathways. Ruddy-headed geese could act as umbrella species determining the minimum size for conservation areas, selecting sites to be included in reserve networks, and setting minimum standards for the composition, structure, and processes of ecosystems.
A greater understanding of the mechanisms involved in influencing the collision risk for this endangered species is essential if the situation is to be managed effectively. As the number of wind farms increases, the need for effective mitigation measures becomes more and more important, particularly in the case of a species where there are serious conservation concerns.
Mitigation measures such as making wind farm and HV network areas unattractive for foraging – while offering attractive habitat outside these places – will probably reduce the amount of time the birds spend inside risk areas as suggested by (Grajetzky and Nehls 2017). Other approaches used to minimize turbine collision include temporary turbine shut-downs upon approach by threatened species, such as the California Condors Gymnogyps californianus (Watson 2018).
Our results suggest that high-density areas of Ruddy-headed goose are characterised mainly by low-lands with high productivity indices near watercourses and waterbodies. Therefore, the new installation of wind farms and power networks should avoid areas with these environmental conditions along the Atlantic Coast. Hence, it is important to evaluate the landscape configuration before and after construction against the behavioural trade-offs the birds have to make to utilize patches, such as foraging patch quality and perceived predation risks as well as travel costs (in terms of energetic costs and predation risk) (Jensen et al. 2008; Tombre et al. 2008). In this sense, applying predictive models and future scenarios could help predict land-use and climate changes (Nicholson et al. 2019). The planning of new wind farms should consider these future scenarios to reduce long-term negative effects, help assess cumulative impacts, and develop efficient management plans.
Ruddy-headed geese perform spring migration mainly over land, and this might be seen as a huge threat for the species. Spring migration is also faster than autumn migration and tracked geese arrive at their breeding sites less than two weeks after departing their wintering grounds (Pedrana et al. 2020). Therefore, one mitigation measure might be to shutdown turbines during this period (between 12 August and 15 September). Understanding when and how environmental predictors affect the decision to start spring migration could help to improve this mitigation measure.
Wind energy production is necessary to mitigate the effects of global warming. However, increasing wind power production needs to be accompanied by scientifically justified mitigation measures to minimise negative effects on wildlife. Therefore, there is an urgent need to identify important areas, and to designate them as protected areas so that informed decisions can be made on the location of wind farm developments. For instance, core areas during migration such as the ones identified in this study along the Patagonia coastline should not be considered for new developments. Research and monitoring should be implemented by the national government and the wind energy industry, in consultation with relevant experts, to expand our understanding of the impacts of wind farms. This will be an iterative process that will inform decision-making, appropriate site selection and wind farm design. Some of the topics that should be encompassed in research and monitoring requirements are the following: effects and potential population level impacts on birds of disturbance displacement, barriers to movement, collision mortality, habitat loss or damage and the effectiveness of different wind farm layouts and turbine designs to provide mitigation.