Wilsons Petrel breeds in vast numbers with recent population estimates of 30,000,000 on the Antarctic continent and sub Antarctic islands from Cape Horn (Chile) to Kerguelen Islands (French Southern Territories) during the northern winter and small numbers migrate into the northern Atlantic after the breeding season.
Wilsons is a small to medium-sized storm petrel with an evenly proportioned body. It is best distinguished other Petrels by its flight pattern which can be described as hirundine-like. Its flight is purposeful and direct with continually flapping wings on uniquely stiff wing-beats. It forages methodically, skimming low over the water with shallow stiff wing beats interspersed with sustained searching glides.
The species typically collects food by hanging over the prey item sometimes for long periods with the wings held in a shallow V stabilising by foot pattering on long spindly legs. Wilsons Petrel skilfully dances over the waves, making both Leaches and Storm Petrels appear rather clumsy.
On close views, typically less than 20 feet it is possible to see the yellow webbing between the toes. The species has broad wings and pointed wing tips, the leading edge lacks a sharp angular bend at the carpal joint and the trailing edge is uniquely straight amongst 'our' storm petrels. The tail is long and there is normally an obvious toe projection beyond the tail tip. Wilsons has obvious pale broad upperwing-covert bars and a white wrap-around rump patch.
Historical analysis of Irish records
By the end of 2008 a total of 110 records had been accepted for Wilsons Petrel (note that the 'at sea' records are excluded from the total), with the main bulk of sightings during the 6 week period 18 July-28 Aug.
The species was admitted on to the Irish list courtesy of 2 birds obtained in 1891 from counties Fermanagh and Down but Wilsons Petrel has until recently been rare in Irish waters. Though annual since 1998 there have been records from 1962 when it was believed that long deep water pelagic trips were the only way to see the species.
However with a growing understanding of Petrel identification the species can almost be expected from seawatch points and pelagic trips.
Typically a strong NW blow, force 3-4 with associated squalls are the essential ingredients for seawatching from Brandon Pt and nearby Deelick Pt.
However some of the Wilsons seen over the years (listed below) have been observed during calm weather and warm sunny conditions.
1999 (2) Brandon Pt 20 July - (1) Brandon Pt 14 Aug
2004 (3) Brandon Pt 29 Aug - (1) Brandon Pt 11 Sept
2005 (1) Brandon Pt 18 July - (2) Brandon Pt 25 Aug
2006 (2) Brandon Pt 21 June - (1) Brandon Pt 06 Sept
2007 (1) Brandon Pt 24 Sept
2009 (14) Brandon Pt 01 Aug - (2) Brandon Pt 28 Aug
The short range inshore trips which I have been organising annually since 1998 have been very successful and prove that the species is guaranteed off the SW/W coast annually in small numbers.
A lot of patience and luck is required for those venturing out offshore but equally a versatile boat with skipper and a powerful chum mixture are also essential. Thankfully I have been lucky over the years with all these key factors falling into place, perhaps the only item which I have no control over the weather which has been very kind on most if not all of the days in question.
The method used on my pelagic trips is a simple wait and see; by creating an oil slick and adding chum the boat drifts with the current and all on board keep a constant look out for interesting birds especially Wilsons Petrel.
1998 (2) 6km off Inistearaght 08 Aug [26th Irish record]
2002 (4) 8km off Inistearaght 06 Aug
2004 (3) 8-10 km off Inistearaght 14 Aug
2005 (1) 10km WSW Inistearaght 09 Aug
2006 (1) 7km W Inistearaght 08 Aug
2007 (1) 8km SW Inistearaght 27 Aug
2008 (15+) 60 km SW Valentia 21 Sept - (15+) 60 km SW Blasket Islands 25 Sept
2009 (6) 10 km SW Inistearaght 07 Aug - (1) 160 miles W Blasket Islands 20 Aug
2010 (2) 9km SW Inistearaght 10 Aug