Black Petrel - Description

Description

• All black except for pale sections on bill
• Medium-sized petrel (average about 700 g)
• Wingspan averages 110 cm
• Often seen in the outer Hauraki Gulf, New Zealand from October to May
• Oldest banded bird recorded is 29 years (E. Bell, pers. comm.)

Breeding sites:

• Endemic to New Zealand - previously found throughout North Island and Northwest Nelson but predators (feral cats, pigs) caused their extinction on the mainland from about the 1950s (Medway 2002)
• Now restricted to main colony on Great Barrier Island (c. 5000 birds over summer, including approximately 1300 breeding pairs and 1000 “pre-breeders” seeking mates (Bell et al. 2011)
• Small colony present on Little Barrier Island of c. 250 birds (Imber 1987)

Population decline:

• Classed under DOC Threat Classification System as Nationally Vulnerable (Miskelly et al. 2008) and by the International Union for Conservation of Nature or IUCN Red list: Vulnerable
• Land-based population research at their breeding colonies since 1995 indicates the species is declining at a rate of at least 1.4% per year (Bell et al. In press A)
• At current survival rates, a fledged bird has a 1 in 20 chance of reaching breeding age (4+ years) and must breed 20 times successfully just to replace the current population.

Breeding:

• Breeding takes place from October to June in the Hauraki Gulf
• Adults return to the colony in mid-October to clean burrows, pair and mate with the same partner (Imber 1987)
• Males will return to the same burrow every year and try to attract another female if their mate does not return or if there is a “divorce” (about 12% annually) (Bell et al. 2011)
• Pairs then depart on “honeymoon”, returning to the colony again in late November when the females lay a single egg (Imber 1987)
• Both birds share incubation of the egg for 57 days (about 8 weeks) (Imber 1987)
• Eggs can hatch from late January through February (Imber 1987)
• Chicks fledge after 107 days (15 weeks) from mid-April through to late June (Imber 1987) - about 75% of chicks survive to fledge (Bell et al. 2011)
• In 2011 breeding success fell to 61% (Bell, unpublished data) for unknown reasons
• Adults and chicks migrate to South America for winter (to waters off the Ecuador coast) (Imber 1987, Bell et al. In press B) – only 10% of fledged chicks survive this first year
• Juveniles will remain at sea in the West Pacific for 3–4 years until they are ready to breed – survival rate is 46% during this time vs 90% for birds over 3 years old (Bell et al. 2011)
• At about 4 years old, pre-breeding birds will fly back to the colony to find a mate – this may take 1-2 seasons (Bell et al. 2011)

Range while at sea:

• In addition to breeding birds, there are likely to be a further 6000 juveniles, pre-breeders and non-breeding birds at sea
• Black petrels may range from the east coast of Australia all the way to the coast of South America between Mexico and Peru and the Galapagos islands (Bell et al. In press B)
• Females and males forage separately and in different places – it is not known why (Bell et al. 2009, Bell et al. In press B)
• Birds forage much closer to the Hauraki Gulf over the summer and autumn while incubating an egg and raising a chick – mainly in the Tasman Sea and to the North East of NZ (Bell et al. 2009, Bell et al. In press B)
• They may feed at night or during the day (unlike albatrosses which do not feed at night) (Imber 1976)
• Birds will aggressively follow fishing boats and long line hooks and may dive up to 20m below the surface after baits (Imber 1976)
• Black petrels can cover amazing distances – the longest recorded foraging trip for a bird from Great Barrier is 39 days (Bell et al. 2009, Bell et al. In press)
• Mapping of foraging patterns against fishing activity in NZ waters is currently underway (see reports – Bell et al. 2009, Bell et al. In press).