heat. The eggs are three to four times bigger than chicken eggs. Ideally, the eggs are incubated in a burrow dug into the guano layer (which provides suitable temperature regulation), but the widespread human removal of guano deposits has rendered this type of nest unfeasible in many colonies. To compensate, penguins burrow holes in the sand, nest under rocks or bushes or make use of nest boxes if they are provided. The penguins spend three weeks on land caring for their offspring, after which chicks may be left alone during the day while the parents forage. The chicks are frequently killed by predators or succumb to the hot sun. Parents usually feed hatchlings during dusk or dawn. In 2015, when foraging conditions were favourable, more male than female African penguin chicks were produced in the colony on Bird Island. Male chicks also had higher growth rates and fledging mass and therefore may have higher post-fledging survival than females. This, coupled with higher adult female mortality in this species, may result in a male-biased adult sex ratio and may indicate that conservation strategies focused on benefiting female African penguins may be necessary. Predation The average lifespan of an African penguin is 10 to around 25 years in the wild and up to 30 in captivity. The primary predators of African penguins at sea include sharks and fur seals. While nesting: kelp gulls, Cape genets, mongooses, caracals and domestic cats and dogs may prey on the penguins and their chicks. Mortality from terrestrial predators is higher if penguins are forced to breed in the open in the absence of suitable burrows or nest boxes. Threats and conservation Historical exploitation African penguin eggs were considered a delicacy and were still being eaten and collected for sale as recently as the 1970s. In the 1950s, they were being collected from Dassen Island and sold in nearby towns. In 1953, 12,000 eggs were collected. In the late 1950s, some French chefs expressed interest in recipes including African penguin eggs collected from the islands off the west coast of South Africa and placed annual orders for small quantities. In the mid 1960s, eggs were collected in the thousands and sold by the dozen, with each customer limited to two dozen eggs in total. The practice of collecting African penguin eggs involved smashing those found a few days before a collecting effort to ensure that only freshly