Missing for the last twenty years: the case of the southernmost populations of the Tropical Mockingbird Mimus gilvus (Passeriformes: Mimidae)

Mariana S Zanon,Maria Alice S Alves,Mariana M Vale

doi:10.1590/s1984-46702015000100001

Abstract

The Tropical Mockingbird Mimus gilvus (Vieillot, 1808) is a widespread species in the Neotropics, but its southernmost populations in Brazil are ecologically (and possibly taxonomically) distinct, occurring only along the coast in restinga vegetation. Once considered the most common bird in restinga, it is becoming increasingly rare, likely due to habitat loss and illegal capture of nestlings. We conducted field surveys to provide an up-to-date distribution of the Tropical Mockingbird in the southernmost portion of the species' range, in the state of Rio de Janeiro, supplying an estimate of its current regional population size and conservation status. We surveyed 21 restinga remnants in Rio de Janeiro, covering all major restinga areas in the state. For sites where the species' presence was confirmed through transect line surveys, we estimated the local population size. The species was found at only four sites. The mean local population density was 52 individuals per km-2. The estimated current and historical Extent of Occurrence (EOO) were 256 km2 and 653 km2, respectively. Combining the population size and EOO results, we estimated that the population of the state of Rio de Janeiro currently ranges from 2,662 to 13,312 individuals, corresponding to an estimated reduction of 61% to 92% in population size in the last 20 years. The species, therefore, can be considered Endangered in the state of Rio de Janeiro. We recommend that a taxonomic study of the southernmost populations is carried out in order to clarify whether they represent a different, likely threatened species. We also recommend that the environmental regulations that protect restingas are used towards the protection of these populations.

Highlights

The Tropical Mockingbird, Mimus gilvus (Vieillot, 1808), is widespread in the Neotropics, but some of its populations at the southernmost edge of its distribution are disappearing
In spite of occupying most of the South American continent, in the eastern coast of Brazil the Tropical Mockingbird only occurs in restinga (SICK 2001), an ecosystem of the Atlantic Forest biome that is located between the forest and the sea, and is mainly composed of sandy coastal plains (ARAUJO 1992)
The westernmost limit of the Tropical Mockingbird in the state of Rio de Janeiro is still Marambaia, but its easternmost limit has retreated to the Restinga de Jurubatiba, and gaps have appeared in the middle of its distribution (Fig. 3)

Summary

Introduction

The Tropical Mockingbird, Mimus gilvus (Vieillot, 1808), is widespread in the Neotropics, but some of its populations at the southernmost edge of its distribution are disappearing. We conducted field surveys of the Tropical Mockingbird to provide up-to-date occurrence records in the southernmost portion of its range, in the state of Rio de Janeiro, and to supply an estimate of the current size of its population in the state. We used this information to reassess the species’ conservation status at the state level, based on two IUCN criteria: Extent of Occurrence and Population Size (IUCN 2001)

Methods

Results

Conclusion