Northern gannet

Morus bassanus

Photo by Andreas Trepte (Wikipedia)

Common name:
northern gannet (en); ganso-patola (pt); fou de Bassan (fr); alcatraz común (es); basstölpel (de)

Taxonomy:
Order Pelecaniformes
Family Sulidae

Range:
The northern gannet is found in the northern Atlantic, from Greenland south along the coasts of Europe, north-western Africa and North America down to Cuba and Senegal.

Size:
These birds are 80-110 cm long and have a wingspan of 165-190 cm. They weigh 2,2-3,6 kg.

Habitat:
The northern gannet is found in coastal and marine waters, never very far from the coast. They breed in steep cliffs or uninhabited offshore islands.

Diet:
They feed on pelagic shoaling fish, which they catch by plunge-diving from considerable heights. They often feed in association with predatory fish and cetaceans, such bluefish and dolphins. Their main prey are mackerel and herring, but also capelin, coalfish, cod, whiting, haddock, sprat, pilchard, garfish, sandlance, sandeel, smelt, menhaden and flounder, typically smaller than 30 cm. They can also eat some squids and shrimps.

Breeding:
Northern gannets breed in March-September. They are monogamous and pair for life. The nest is a mound of seaweed, feathers and plant materials, placed in a rocky cliff or island always near the ocean. The female lays a single pale blue-green chalky egg, which is incubated by both parents for 42-46 days. The chicks fledge 3 months after hatching. Each pair raises a single chick per season, which will reach sexual maturity after 3 years.

Conservation:
IUCN status - LC (Least Concern)
This species has an extremely large breeding range and the global population is estimated at 950.000-1.200.000 individuals. Although they suffer some mortality from entanglement in nets and other fishing gear, the population in North America in known to be increasing at a rate of 3-3,5% per year, while the population is Europe seems to be stable.

Peruvian booby

Sula variegata

Photo by Alejandro Tabini (Birding Peru)

Common name:

Peruvian booby (en); atobá-peruano (pt); fou varié (fr); alcatraz piquero (es); guanotölpel (de)

Taxonomy:

Order Pelecaniformes

Family Sulidae

Range:

The Peruvian booby is found in the area of the Humboldt Current, breeding from Punta Pariñas , in northern Peru, to Concepción, in central Chile. Non-breeders can be found as far as south-west Ecuador.

Size:

The Peruvian booby is 71-76 cm long

Habitat:

This strictly marine species feeds close to the coast in cool, rich waters of upwellings where food is abundant. They breed in bare, arid islets along rocky coasts, mostly on cliff ledges in Chile, but preferring open, flat ground in Peru.

Diet:

This fish eater feeds almost exclusively on the abundant supplies of anchoveta (Engraulis ringens) found in their range, but will switch to other fish species, including sardine (Sardinops), mackerel (Scomber), and other fish, when stocks collapse. Feeding mostly occurs by plunge-diving from moderate height.

Breeding:

Peruvian Boobies breed throughout the year, but the main breeding season takes place during the austral spring and summer, in September-March. They nest on the ground, in a bowl made of guano where the female lays 1-4 pale blue eggs. The eggs are incubated by both adults for 4-5 weeks and the chick rearing period lasts about 3 months. Most pairs may attempt to breed for a second time during the year depending on food availability.

Conservation:

IUCN status - LC (Least Concern)

With a global population estimated at 1,2 million and a large breeding range, this species is not considered threatened at present. Still, the population is suspected to be fluctuating owing to fluctuations in prey populations, and El Niño events may cause dramatic mortality events in some years.