Accurate data on the population size and conservation status of the Madeira storm-petrel has proved difficult to obtain, in part because of its nocturnal and burrow-nesting habits, which make surveys challenging (5). However, population declines have been observed in some areas, such as in Europe, where its breeding population underwent a moderate decline between 1970 and 1990 (11), and in Japan, where one colony was reduced from 25,000 pairs in the mid-1960s to only 800 pairs by 1994. The cause of these declines was likely to be a combination of human exploitation and habitat degradation (5).
The Madeira storm-petrel has long been hunted for food. In the Eastern Atlantic, human predation on seabirds occurred until recently, especially in the Azores and on Saint Helena, and is likely continue to a small degree in Madeira. On large islands, habitat degradation has also severely reduced populations, meaning most now occur on small, isolated offshore islets. Continued development and degradation on the larger islands prevents recolonisation, thus leaving populations restricted to small patches of habitat with limited numbers of breeding sites. The development of artificial structures, such as buildings, also causes collisions, especially where there are bright lights to attract birds. This is thought to be a significant cause of juvenile mortality in the Madeira storm-petrel (5).
On some islands, the Madeira storm-petrel is further threatened by predation by introduced mammals such as rats and cats (2) (5). Introduced sheep and goats may also trample burrows and, along with introduced rabbits, can overgraze vegetation, leading to erosion and landslides and causing burrows to collapse (5).