A survey for the Sierra Madre Sparrow ( Xenospiza baileyi ), with its rediscovery in the state of Durango, Mexico

Abstract

The Sierra Madre Sparrow (Xenospiza baileyi) is a highly endangered and endemic species of the highlands of south-central Mexico, where it is resident in bunchgrass (Gramineae) and adjacent marshy habitats in the southern Sierra Madre Occidental (Jalisco and Durango states) and in the mountains around the Valley of Mexico (Distrito Federal and the states of Morelos and Mexico). This species was first collected in the southern part of this range on 23 April 1945 at La Cima, D.F., where its persistence has been documented essentially continuously since 1951. The first specimens of the taxon were collected in the Sierra de Bolaños of extreme northern Jalisco on 3–10 March 1889, including the type from which the genus and species were described in 1931. Two populations have been found in southern Durango: one 30 miles (48 km) south-west of the City of Durango on 22 March 1931, and the other 5 miles (8 km) west of El Salto on 16–17 June 1951. The Sierra Madre Sparrow has not been otherwise confirmed in the northern part of its range, which in July 2004 led us to conduct an extensive search for it in these areas of Durango and Jalisco as well as south-western Zacatecas. Here we present the findings from that search, during which several sites were intensively surveyed and a single population of this sparrow was located – a new one between the city of Durango and El Salto, Durango. This rediscovery increases possibilities for understanding the biogeography, ecology and basic requirements of the Sierra Madre Sparrow, information of fundamental importance for proposing measures that promote its conservation in any of its remaining populations.

Adaptive genetic diversity and evidence of population genetic structure in the endangered Sierra Madre Sparrow (Xenospiza baileyi)

“…pers. ), and one in Mexico City and Morelos where it occurs in the Trans-Mexican Volcanic Belt (TVB) [37,38]. Ecological niche modeling [39] reported no significant ecological dissimilarity between the northern versus southern population localities.…”

“…precipitation, temperature, and elevation), where the larger southern population was more restricted ecologically. Further, this species is a habitat-restricted, inhabiting patches of subalpine bunch grasslands (Muhlenbergia spp., Festuca spp., Calamagrostis tolucensis., and Stipa ichu) isolated among pine forests [38,40,41]. Sierra Madre Sparrows were historically distributed more widely, and in a patchy form, in both the SMOc and TVB, but no evidence exists for a historic connection between these areas.…”

“…[39,[42][43][44]. Moreover, the Sierra Madre Sparrow has suffered a dramatic habitat reduction owing to anthropogenic land-use modifications, including urbanization, agriculture, and livestock grazing [37,38,41,45,46]. This habitat reduction has been more pronounced in the northern population [38], although bunchgrass areas from the southern Valley of Mexico populations have also been affected.…”

“…These changes have caused documented historical (in Jalisco, Durango, Morelos and Mexico City) and recent (Ojo de Agua El Cazador, Durango) local extinctions (Fig 1). As a measure of the speed at which human activities continue to impact the Sierra Madre Sparrow, the Ojo de Agua El Cazador population was discovered just 15 years ago [38] with a maximum observed number of 18 sparrows [47], and where the last observation of this species was recorded in 2013 (C. Aguirre-Calderón comm. pers.).…”

“…Another possible explanation may be related to more recent events, such as human-driven habitat fragmentation. As there is no documented evidence of geographic connectivity between Sierra Madre Sparrow distributional areas [37,38,43], initial habitat fragmentation into two populations would likely have occurred more than 150 years ago, prior to the oldest recorded specimens (1889). And, considering the rich history of specimen collection in Mexico during the 19th and 20th centuries [94], evidence of connecting populations would probably have been documented [42][43][44].…”