Introduction

Wetlands play a key role for wildlife and function as habitats for numerous endemic, resident, or migratory species (^{Serrano et al. 2013}). On a global scale, they are considered one of the ecosystems with greatest biological diversity (^{Valiente et al. 2015}). In particular, the coastal and continental wetlands in arid zones of Mexico are important stop-over and wintering sites for migratory birds, such as the Marbled Godwit (Limosa fedoa).

The Marbled Godwit breeds in northern USA and southern Canada, migrating to the coasts of USA and Mexico (^{Shaffer et al. 2019}), but has also been recorded as far south as Chile (^{Martínez-Piña & González-Cifuentes 2004}). In Mexico, the Marbled Godwit is considered a threatened migratory species (^{SEMARNAT 2010}), with a distribution mainly constrained to the Atlantic and Pacific coasts (^{Ramírez-Bastida & Navarro-Sigüenza 2013}). The species is a shorebird that is frequently sighted in marine areas (^{eBird 2024}). However, the Marbled Godwit has also been recorded in mainland Mexico, in the states of Chihuahua, Coahuila, Durango, Guanajuato, Jalisco, Michoacán, Querétaro, State of Mexico and Mexico City (^{eBird 2024}; ^{iNaturalistMX 2024}). For San Luis Potosí, the easternmost tip of the state shows up as a potential area for presence of this species (^{Ramírez-Bastida & Navarro-Sigüenza 2013}).

Nevertheless, there is an absence of records of the species in the Potosino-Zacatecano Plateau (^{iNaturalistMX 2024}). Studies of aquatic birds are scarce in this region and tend to present isolated records, highlighting the need to carry out detailed studies over longer temporal and spatial scales (^{Sigala-Meza et al. 2022}). Here, we present a record of the Marbled Godwit in the Potosino-Zacatecano Plateau, in San Luis Potosí, and review existing records in mainland Mexico to update information on the species’ distribution.

Methods

Study site

Our observations were conducted in Salinas Lagoon, also known as Santa María Lagoon, adjacent to the urban area of Salinas de Hidalgo, San Luis Potosí, Mexico (Figure 1). This area occurs within the biogeographical sub-province of the Potosino-Zacatecano Plateau, which is found in the central and western part of the state. There is a scarcity of water in the state, and waterbodies are scattered and temporal, as they depend on precipitation from the previous year (^{Luévano et al. 2010}), and may totally evaporate during severe drought episodes. Salinas Lagoon is a salty water lagoon that is one of the most prominent waterbodies in the municipality, and bears water for most of the year.

Figure 1 Location of the study area (municipality of Salinas) 

However, in the summer of 2023, precipitation in June-September was 19% of the mean rainfall values for these months during the 1976-2023 period (^{SMN 2024}), resulting in a severe drought during which the lagoon dried out. Conversely, when the rainy season arrives, precipitation is typically intense, so many waterbodies form, which are crucial for several taxonomic groups, such as amphibians, reptiles, birds, and mammals. Within the avian group, it is noteworthy that such temporal lagoons can attract multiple aquatic or semiaquatic birds. In total, 62 bird species were spotted in Salinas Lagoon during our surveys, among which the Black-necked Stilt (Himantopus mexicanus), American Avocet (Recurvirostra americana), Northern Shoveler (Spatula clypeata) and the Killdeer (Charadrius vociferus) stand out. This highlights the importance of this lagoon, which functions as an oasis in the middle of a semidesert.

Results

On 27 August 2023 at 06:59 h, we observed a single individual of the Marbled Godwit at a distance of approximately 50 m, in Salinas Lagoon (Figure 2), at a latitude of 22.6334682597, a longitude of -101.7200359087 and an altitude of 2069 m a.s.l. The species was distinguished by its large size and long bill, with a pinkish base that got darker and slightly upwardly curved at the tip (^{eBird 2024}). The individual had predominantly brown feathers and considerably long legs. The photograph of this individual was registered in the digital ornithological collection of the Museum Alfonso L. Herrera, at the Universidad Nacional Autónoma de México, in Mexico City, under the voucher number FV-04220. The individual was observed resting in this semi-permanent, salty lagoon (Figure 2), and was present with other species, such as the Black-necked Stilt (Himantopus mexicanus) and the American Avocet (Recurvirostra americana).

Figure 2 Marbled Godwit (Limosa fedoa) photographed in Salinas (Santa María) Lagoon, San Luis Potosí. Photograph taken by Jesús Lenin Lara-Galván on 27 August 2023. 

Using the ^{eBird (2024)} and ^{iNaturalistMX (2024)} electronic databases, we compiled a total of 39 continental records of the Marbled Godwit in 10 Mexican states for the 2014-2024 period. These continental records were restricted to the centre-north of the country, with Mexico City and the State of Mexico having the southernmost mainland records (Figure 3). Similarly, of the 39 records, 25 occurred in the months of October to February (64.1%), and 14 from March to September (35.9%). More specifically, the month of November registered most of the mainland sightings (n = 9 sightings; 23.1%). Other months with a considerable number of sightings were February and July, with five each (12.8%), as well as August, September and December with four each (10.3%). Therefore, most of the mainland sightings were concentrated in late autumn-winter (November-February), as well as mid and late summer (July-September), which could coincide with the period in which the species migrates. The closest records to the present study were two records located in El Palote Dam, municipality of León, in the state of Guanajuato (^{iNaturalistMX 2024}), 160 km southwards of the present record in straight line (Figure 3). Almost all mainland records of the species were associated with a natural body of water.

Figure 3 Presence records of the Marbled Godwit (Limosa fedoa) in mainland Mexico for the 2014-2024 period. Data retrieved from ^{eBird (2024)} and ^{iNaturalistMX (2024)}. 

Discussion

Our observation represents the first record of a Marbled Godwit in the Potosino-Zacatecano Plateau, San Luis Potosí, in the centre of mainland Mexico, and may be the result of early migration by some individuals. The potential winter distribution of the Marbled Godwit in Mexico occurs mainly on the Pacific coast, in the states of Baja California, Baja California Sur, Sonora, Sinaloa and Nayarit (^{Navarro-Sigüenza & Peterson 2007}). As for the Gulf of Mexico, the coasts of Tamaulipas, Veracruz, and Tabasco have ecological suitability for the species (^{Olson 2011}). This suitability increases in the Yucatán Peninsula, showing western Campeche and northern Yucatán and Quintana Roo states as potential areas of distribution (^{iNaturalistMX 2024}). Moreover, even though the easternmost tip of San Luis Potosí state has potential for presence of this species (^{Ramírez-Bastida & Navarro-Sigüenza 2013}), our record in the Potosino-Zacatecano Plateau is located at the opposite end of the state, where there are no records, and that is not considered within the potential distribution of the species (^{Ramírez-Bastida & Navarro-Sigüenza 2013}).

Notably, our record of the Marbled Godwit in Salinas Lagoon occurred in the summer month of August, whereas the majority of records in the continental mainland were reported for the winter months. ^{Mendoza & Carmona (2013)} registered maximum number of individuals in October, although their focus was on the coastal state of Baja California Sur. Furthermore, the fact that the present, and other mainland records, were all associated with natural waterbodies demonstrates that this species, as with other birds of the Mexican highlands (^{Sigala-Meza et al. 2022}), depends on waterbodies of natural origin. This underlines the relevance of mainland waterbodies in Mexican arid and semi-arid zones, since they facilitate the transit of avian species from one coast to the other (^{Palacio-Núñez et al. 2008}). Indeed, these wetlands act as supply and resting areas that enhance genetic exchange among individuals of different populations. Therefore, the degradation or elimination of these habitats would reduce the survival opportunities of the species during migration (^{Bortels et al. 2011}).

Unfortunately, the urbanisation process, the exploitation of aquifers and climate change bring about severe threats for these waterbodies, causing water quality reduction, or even the disappearance of these oasis of water in an arid landscape. In fact, a loss of water of around 1.44% has been reported in waterbodies in San Luis Potosí (^{CONABIO 2019}), which puts at risk the survival of aquatic bird species. In our study area, the consequence of a shrinking Salinas Lagoon can be even more devastating for species that require water-bodies of high salinity. This is the case of the Snowy Plover (Charadrius alexandrinus), which has been reported to breed in Salinas Lagoon (^{Luévano et al. 2010}).

Consequently, Salinas Lagoon has an evident relevance for the survival and migration of birds at different periods of the year. However, the site is not protected, and as a result waste water dumping and soil degradation occur in the area, which could put at risk the quality of water in this lagoon. Therefore, we propose establishing protection of the lagoon, initially at a municipal level, and encourage further studies to support a greater degree of protection in the future. Thus, the lagoon would act as a priority area exclusively used by wildlife, which could minimize anthropogenic activities, and promote the conservation of biodiversity in this small yet extremely valuable wetland.