On Socorro, it breeds in rocky burrows within dense bushy areas at the forest edge. Breeding is concentrated above 700 m (Brooke 2004), but observations in 1981 suggested that the major breeding sites were at 500-650 m. Birds have been seen roosting in the naval base at Cape Rule (J. Martínez Gómez in litt. 1998, 1999, 2000). On Clarión, it nested in burrows on grassy and bracken-covered slopes (S. N. G. Howell in litt. 1998). Birds return to colonies in mid-November with breeding from late January to mid-March (Carboneras et al. 2014).

Puffinus auricularis breeds around Cerro Evermann on Socorro in the Revillagigedo Islands, Mexico. In 1981, the population was estimated at 1,000 pairs, with more found in the north of the island in 1990. In 1993-1999, the estimate was 500 pairs (J. Martínez Gómez in litt. 1998, 1999, 2000). In 2008, fewer than 100 breeding pairs could be located (J. Martínez-Gomez in litt. 2007, 2008, 2009). However, 46,000 individuals (95% CI = 18,000-89,000), including 10,600 breeding birds, were estimated during at-sea censuses in 1980-1994 (Spear et al. 1995). It is clear that the breeding range has contracted, and threats indicate that numbers have declined. The species formerly bred on Clarión and San Benedicto, but was almost certainly extinct on the former by 1988, and there has been no confirmed breeding on the latter since 1952. Birds seen immediately north of San Benedicto in 1988 and 1990 provide some hope that a population remains. In the non-breeding season, it forages largely in waters over the continental shelf of Mexico (Spear et al. 1995).

Conservation Actions Underway
In 1994, the Revillagigedo Islands were declared a Biosphere Reserve. There are plans to conduct surveys on Clarión and Socorro, with intensive cat-trapping taking place in 2007, but previous efforts have been poorly resourced (B. Tershy and B. Keitt in litt. 1999, J. Martínez-Gomez in litt. 2007, 2008, 2009). Pigs and sheep were eradicated from Clarión between 2001 and 2004, but attempted rabbit eradication failed. The eradication of sheep from Socorro began in 2009 and should be complete within a few years (A. Aguirre in litt. 2012). Similarly, cat eradication is underway on Socorro (A. Aguirre in litt. 2012). The installation of an automated playback system to assist the recolonisation of Clarión is under consideration (B. Tershy and B. Keitt in litt. 1999).

Conservation Actions Proposed
Eradicate introduced mammals on Socorro and Clarión. Determine whether a breeding population remains on San Benedicto. Assist the recolonisation of Clarión. Continue to monitor numbers on Socorro and at sea. Conduct high-level lobbying to raise awareness of the effect military operations may have on the species.