Procellariidae Shearwaters and Petrels
Version: 1.0 — Published March 4, 2020
Introduction
Hundreds of millions of shearwaters and petrels spread out every year after breeding, following oceanic currents in great loops that span the Earth. These masters of dynamic soaring, varying in size from the thrush-sized prions to the albatross-sized giant petrels, can cover the oceans more efficiently than anything human-engineered. With diets and habits as diverse as their sizes, and an exquisite sense of smell typical of many in this order, these mariners can find planktonic prey across the featureless main. The same olfactory acuity guides them to their individual nesting burrows among many thousands of others. That they come back home with such precision has allowed the diversification of species across the islands of the world.
Habitat
Procellariids inhabit open oceans worldwide except when breeding. They usually breed on small islands far from the mainland that are, or at least were originally, predator free.
Diet and Foraging
Most species feed primarily on small aquatic invertebrates and fish. Many of the petrels and prions grasp prey from the water while in flight, and many shearwaters dive for prey from the water surface. Some Pachyptila species have comb-like lamellae on the bill, and they filter for zooplankton at the surface either while sitting or sometimes while propelling themselves along the water surface with their feet and wings, mouth submerged. Pelecanoides species, similar in appearance and feeding behavior to murrelets (Alcidae), are distinctively able to dive from the air and pursue prey underwater all in one motion. The largest species (Macronectes) feed on carrion of large vertebrates and are active predators of colonial seabird eggs and chicks.
Breeding
Procellariids are monogamous, often meeting the same mate at their nest site for many years in succession. Most species of procellariids nest in burrows or crevices, though Macronectes species build mounds of vegetation on the ground and Fulmarus species nest on cliff ledges. Many burrow-nesters nest in remote slopes, sometimes as much as 30 km from, and hundreds of meters above, the sea. Females lay a single egg, which is incubated for six to nine weeks, longer in the larger species. Both parents participate in the construction of the nest, both incubate the egg on incubation shifts of two days to two weeks, and both feed the chick. The chick is brooded at first, for up to 20 days in some species; then the parents cease brooding and visit the chick only to feed it. The parents often intersperse short feeding trips (at intervals of a few days) with long trips (at intervals more like a week), the end result from the chick’s perspective being that it receives food from the parents every couple of nights or so for most of its development. Most chicks fledge and disappear out to sea at three to four months post-hatch.
Conservation Status
At least 50 petrel species (54%) are of conservation concern because of pressure on the breeding grounds (from hunting, introduced predators, or habitat destruction) or because they are bycatch in commercial fisheries (9 NT, 20 VU, 12 EN, 8 CR, 1 CR(PE)). Because many procellariids breed on only one or a few small islands, even the most abundant species are extremely vulnerable to stochastic events, habitat alteration, and the introduction of non-native predators. In addition to having small breeding ranges, procellariids are slow to reproduce, producing only a single egg per pair, and do not reach maturity for several years after fledging. This predisposes a population to slow growth and recovery following a decline. Although there are only two documented extinctions of petrels in recent history, one species, the Jamaican Petrel Pterodroma caribbaea, is considered critically endangered and is very likely extinct; it has not been recorded since 1879. Conservation plans, in place for many species, include the removal of non-native predators, reintroduction to additional islands, habitat restoration, and regulation of fishing practices.
Systematics History
Procellariidae is in the order Procellariiformes. The diving-petrels were long thought to be sister to the shearwaters and petrels, but current evidence indicates that Pelecanoides is embedded within Procellariidae (Kennedy & Page 2002, Mayr 2009). Procellariidae is closely related to the two families of storm-petrels, but it remains unclear whether it is sister to Oceanitidae or Hydrobatidae. The clade made up of Procellariidae together with either Hydrobatidae or Oceanitidae is in turn sister to Diomedeidae (Kennedy & Page 2002, Hackett et al. 2008). Morphological evidence supports the findings of Hackett et al. (2008), indicating Oceanitidae as sister to the rest of the procellariforms and Procellariidae being more closely related to Hydrobatidae and Diomedeidae (Forbes 1882, Mayr 2009).
Conservation Status
Least Concern |
39.8%
|
---|---|
Near Threatened |
10.2%
|
Vulnerable |
17.3%
|
Endangered |
10.2%
|
Critically Endangered |
12.2%
|
Extinct in the Wild |
0%
|
Extinct |
2%
|
Not Evaluated |
0%
|
Data Deficient |
0%
|
Unknown |
8.2%
|
Data provided by IUCN (2023) Red List. More information