[order] PROCELLARIIFORMES | [family] Procellariidae | [latin] Pterodroma externa | [authority] Salvin, 1875 | [UK] Juan Fernandez Petrel | [FR] Petrel de Juan Fernandez | [DE] Salvin-Sturmvogel | [ES] Petrel de las Juan Fernandez | [NL] Witnekstormvogel
| Genus |
Species |
subspecies |
Region |
Range |
| Pterodroma |
externa |
|
PO |
e |
Genus
Genus Pterodroma, Pseudobulweria and Aphrodroma are also knwon as the Gadfly Petrels. They vary in size from rather small birds such as the Cookilaria-species, measuring about 26 cm, to the much larger and robust representatives of this group like the White-headed Petrel with an overall length of about 43 cm. Their plumages also vary a great deal from species to species; from completely black to light grey mantles and pure white bellies, and with different color phases within species. One feature shared by all of them is the black bill of which the shape also shows much variation. Some species are extremely rare and restricted to a very limited area, other are abundant and wander widely or have unknown pelagic ranges.
The group of the Gadfly Petrels counts over 35 species, mainly from the Southern Hemisphere. There are three genera: Pterodroma with about 30 species, Pseudobulweria counting four and Aphrodroma with only one. Many authors have tried to classify the large number of species of this group and to determine their relationships. This has resulted in a division in several subgenera and the grouping of several species which are considered to have a more or less close relationship. The taxonomic discussion has not come to an end yet: new species have been added or split recently and probably will be in the near future.
Large, grey-and-white petrel. Black cap extends to below eyes while white of throat may extend up behind eyes, enhancing capped appearance. Grey upperparts and upperwing, with black “M” across wings. Base of grey tail can show whitish horseshoe. White underparts. White underwing with narrow black trailing edge, black tip, narrow black edge to leading edge distal to carpal joint and then short, bolder, black bar extending from joint towards centre of wing
| wingspan min.: |
95 |
cm |
wingspan max.: |
97 |
cm |
| size min.: |
41 |
cm |
size max.: |
45 |
cm |
| incubation min.: |
57 |
days |
incubation max.: |
63 |
days |
| fledging min.: |
90 |
days |
fledging max.: |
100 |
days |
| broods: |
1 |
|
eggs min.: |
1 |
|
| |
|
|
eggs max.: |
1 |
|
Pacific Ocean : East. Pterodroma externa breeds on Alejandro Selkirk Island in the Juan Fernandez Islands, Chile.
It is highly pelagic, rarely approaching land except at breeding colonies. It nests in burrows on slopes in Dicksonia externa fern-forest and adjacent grasslands at elevations of 600-1,000 m.
It returna to the isolated island to breed in October to November, here they form large breeding colonies. Females lay a single egg in a burrow and the grey, downy chicks hatch in February and March. The chicks are brooded for typically three weeks before being left unattended during the day while their parents go off to feed. The adults return by dusk to their burrows and waiting offspring. Most of the petrel chicks fledge in May and June.
Juan Fernandez petrels spend most of their life out over the oceans, where they search for fish and squid on which to feed. They are often found in areas of upwelling, where cool, nutrient-rich water rises to the surface, resulting in an abundance of prey. They can be seen feeding alongside other seabirds, or occasionally around fishing boats. The Juan Fernandez petrel often depends on sub-surface predators, such as cetaceans and yellowfin tuna, to drive prey to the surface.
Video Juan Fernandez Petrel
httpv://www.youtube.com/watch?v=3e1_nW8PIXc
copyright: Peter Fraser
This species is classified as Vulnerable owing to its very small breeding range, in which it is susceptible to to human impacts and stochastic events. Confirmation that introduced predators are causing a decline would result in an uplisting to Critically Endangered.
The Juan Fernandez petrel appears to face its greatest threats on its tiny breeding island, where numerous introduced species are causing extensive damage to the natural ecosystem, and potentially impacting petrel numbers. Introduced rats, feral cats and coatis pose a significant threat to the Juan Fernandez petrel through predation; rabbits compete for burrows; and cattle trample burrows and may degrade suitable breeding habitat through grazing
Transequatorial migrant, ranging over tropical and subtropical waters of E Pacific, N to Hawaii; occurs regularly off W Mexico. Vagrant to New Zealand and E Australia.
