Tag Archives: Pelagics

Monteiro’s Storm-petrel, August 2013 (Richard Bonser). Note the active wing moult, with the inner primaries dropped.

Monteiro’s Petrel and Pelagic Birding off the Azores

By Peter Alfrey and Richard Bonser

The nine Azorean islands straggle 370 miles of the deep Atlantic, thrusting up from the deep oceanic depths as some of the tallest mountains on earth. The surrounding ocean, through its subsequent varied topography and numerous upwellings, provides rich feeding grounds for migrant seabirds as well as an Azorean endemic species, Monteiro’s Storm-petrel. The aim of this article is to chart the development of pelagic birding in the Azores, along with the species recorded to date, inviting you to consider joining a pelagic expedition.

Pelagic Birding exploration begins

In 2007, Peter Alfrey and Simon Buckell commenced a serious of exploration trips in the waters off the Azores in search of vagrant seabirds. There had already been a few interesting seabird sightings, mainly from the whale-watching boats around the islands – including Black-browed Albatross, Black-capped and Trindade Petrels – and so there was evidently some worth in inaugurating specific trips for seabirds.  The first trips were ‘wild cat’ expeditions from various islands including Corvo, Faial and Santa Maria with seamounts, banks and steep oceanic slopes targeted as likely areas of upwelling of nutrient rich waters, concentrating seabirds.

These first trips discovered good numbers of Wilson’s Storm-petrel, with 30+ at the Azores Bank off Faial in July 2007 and 70-80 also there in September 2009. Regular breeding species were also encountered, including Barolo Shearwater, Bulwer’s Petrels and Grant’s [Band-rumped] Storm-petrels (the winter breeding population), with a new breeding colony of the latter species discovered on Lagoinhas Islet off Santa Maria. Additionally, two Fea’s-type Petrel were recorded but overall, there was not much too significant to write home about.

Various forms of chums were experimented with, and in the end an adapted version of Hadoram Shirihai’s ‘petrel liquor’ was the most successful (using liquid oil instead of melted margarine), along with sardine chum, drip lines and fish oils. Experiments with frozen blocks proved problematic due to the comparatively warm deep Atlantic temperature.

Monteiro’s Storm-petrel- the discovery of a cryptic species endemic to the Azores

In 2008 the ground-breaking paper “Monteiro’s Storm Petrel Oceanodroma monteiroi: a new species from the Azores” by Mark Bolton et al was published in Ibis.  Significantly, this described the summer-breeding population of Band-rumped Storm-petrel on the Azores – Monteiro’s Storm-petrel – as having evolved separately from the winter-breeding population, as already suggested by Monteiro and Furness 1998. Additionally, subtle differences in biometrics, genetics, breeding ecology and vocalisations (Robb et al. 2008) were described, though to the field birder it’s extremely similar to other members of the Band-rumped Storm-petrel complex (see Flood and Fisher 2013, and Howell et al. 2010).

However due to the two populations breeding at different times of year, and with neither apparently spending their respective non-breeding seasons in Azorean waters, the initial way to see Monteiro’s Storm-petrel was simple – visit a colony at the right time of year when only that species was present; May to June in the case of Monteiro’s Storm-petrel. Opportunities for birders to encounter this cryptic species were limited by access restrictions to the main breeding colony off Praia Islet on Graciosa. Joining research teams, who monitored the artificially created nest burrows, used to be the only way. Richard Bonser was lucky to do this in July 2009, courtesy of Joël Bried, and was able to study the species at close range, including adults and nestlings. Remarkably, the two populations use the same nests at times – just as the Monteiro’s Storm-petrels were fledging and leaving their nest sites, the winter population of Band-rumped Storm-petrel (referred to from here on in as Grant’s Storm-petrel) were moving back in.

Monteiro’s Storm-petrel breeding burrows on Praia islet, July 2009 (Richard Bonser)

Monteiro’s Storm-petrel breeding burrows on Praia islet, July 2009 (Richard Bonser)

Monteiro’s Storm-petrel chick, August 2009 (Richard Bonser)

Monteiro’s Storm-petrel chick, August 2009 (Richard Bonser)

And so the waters around Graciosa were the obvious area for pelagic exploration to discover regular feeding areas to see Monteiro’s Storm-petrels at sea. It didn’t take long – in fact, it happened even before the description of the species – as in May 2007, Killian Mullarney and Magnus Robb not only discovered Monteiro’s Storm-petrel at sea to the southeast of Graciosa but also jammed in on a Black-capped Petrel! With a renewed sense of purpose, Peter Alfrey returned to the Azores for seabirding and visited Graciosa in May 2010.

Surveying the sea for Monteiro’s Storm-petrel

Peter Alfrey returned to Graciosa in May 2010, armed with GPS co-ordinates supplied by Killian Mullarney, but adverse weather hampered the potential for any prolonged period at sea. However, in limited searching, Monteiro’s Storm-petrels were found in the same area as in May 2007 and the peaks and troughs of the stormy sea also allowed close approach on a Barolo Shearwater – different from the usual view of a bird flapping frantically away ahead of a boat!

Barolo Shearwater, off Graciosa, May 2010 (Peter Alfrey)

Barolo Shearwater, off Graciosa, May 2010 (Peter Alfrey)

However, other than this close encounter, 2010 was pretty much a mini-disaster. It was getting very expensive too and with boat charter at over 500 euros per day, the only way to make these expeditions cost effective was to literally get more people on board. And so Peter Alfrey returned in June 2011 with a group of 12 birders (including Richard Bonser). However, on the first evening’s pelagic, Peter accidentally dropped £3,000 worth of camera equipment overboard which went straight to the bottom of abyss – negating any perceived cost saving!

The weather conditions in June 2011 were ideal for sailing, but this seemed to have changed the behaviour of the Monteiro’s Storm-petrels. Not many birds could be found in close proximity to the breeding area on Praia islet, and therefore a target area (a bank where fishermen had reported lots of small black and white birds) was visited – the Bank of Fortune – on the last day of the trip. Lying 20 or so miles to the east of Graciosa and providing numerous upwellings suitable for feeding seabirds, it was still within easy reach. Within a few hours of observation, we came across 50+ Monteiro’s Storm-petrels and up to 15 Wilson’s Storm-petrels all at close range.  We also saw at least three Barolo Shearwaters, a Grey Phalarope and four Great Skuas, surprisingly lingering in Azorean waters in early summer. Additionally, a Sooty Tern was also seen on Praia islet where up to two birds have been seen each year recently. That year we also had a Portuguese wildlife film-making crew with us that were filming for a documentary called ‘In Search of Monteiro’s Storm-petrel’, that has subsequently been watched by a quarter of million Portuguese. Not a bad thing for raising the profile of this Azores’ endemic and conserving its breeding habitat.

Monteiro’s Storm-petrel, June 2011 (Gareth Knass). During early summer these hot season breeders are the only ‘band-rumped storm-petrels’ present; the adults show no sign of moult on the primaries and secondaries.

Monteiro’s Storm-petrel, June 2011 (Gareth Knass). During early summer these hot season breeders are the only ‘band-rumped storm-petrels’ present; the adults show no sign of moult on the primaries and secondaries.

Adult Monteiro’s Petrel, June 2011 (Rafael Armada). This is a ‘classic’ Monteiro’s Petrel, photographed in mid-summer when only this species is present in the region, showing a deep forked tail and long-winged appearance producing an overall ‘rakish’ structure. The measurements of Monteiro’s Petrel indicate overall a longer wing and deeper fork to the tail than ‘Grant’s Petrel’.

Adult Monteiro’s Petrel, June 2011 (Rafael Armada). This is a ‘classic’ Monteiro’s Petrel, photographed in mid-summer when only this species is present in the region, showing a deep forked tail and long-winged appearance producing an overall ‘rakish’ structure. The measurements of Monteiro’s Petrel indicate overall a longer wing and deeper fork to the tail than ‘Grant’s Petrel’.

Adult Monteiro’s Petrel, June 2011 (Rafael Armada). Another view of a classic looking bird at the ‘right’ time of year in the ‘right ‘area.

Adult Monteiro’s Petrel, June 2011 (Rafael Armada). Another view of a classic looking bird at the ‘right’ time of year in the ‘right ‘area.

The Bank of Fortune

The last day of our June 2011 pelagic trip established one thing that has become integral going forwards. The Bank of Fortune was the place to locate storm-petrels at sea off the coast of Graciosa. With the world population of Monteiro’s Storm-petrel conservatively estimated at 250 birds, and all of these breeding off Graciosa, the draw of guaranteed sightings of this species would inevitably develop interest from birders. But there was more to come, and we wanted to hit this seabird hotspot at times where we could maximise chances of connecting with vagrants and passage seabirds too.

The obvious choice was to go in the August/September period – the overlap time of year between the hot and cool season breeding ‘band-rumped storm-petrels’, allowing both Monteiro’s and Grant’s Storm-petrels to be seen together. As well as trying to identify these two cryptic species at sea on the basis of wing moult, there was also the real potential of vagrant seabirds…

Monteiro’s Storm-petrel, August 2012 (Peter Alfrey). A worn bird in the start of its primary moult. The upperwing-coverts and dishevelled carpal bar also indicate this bird is in worn plumage.

Monteiro’s Storm-petrel, August 2012 (Peter Alfrey). A worn bird in the start of its primary moult. The upperwing-coverts and dishevelled carpal bar also indicate this bird is in worn plumage.

Monteiro’s Storm-petrel, August 2013 (Richard Bonser). Note the active wing moult, with the inner primaries dropped.

Monteiro’s Storm-petrel, August 2013 (Richard Bonser). Note the active wing moult, with the inner primaries dropped.

Monteiro’s Storm-petrel, August 2012 (Peter Alfrey). Early August is generally too early for Grant’s Storm-petrels to be prospecting nest burrows. However, some Monteiro’s Storm-petrels have also not started to undergo wing moult and therefore both species may show ‘a full set of wings’. In instances such as this, the brownness of the feathering – created by bleaching - suggests a warm season breeder.

Monteiro’s Storm-petrel, August 2012 (Peter Alfrey). Early August is generally too early for Grant’s Storm-petrels to be prospecting nest burrows. However, some Monteiro’s Storm-petrels have also not started to undergo wing moult and therefore both species may show ‘a full set of wings’. In instances such as this, the brownness of the feathering – created by bleaching – suggests a warm season breeder.

‘band-rumped storm-petrel’ off Graciosa, early August 2012 (Vincent Legrand). The fresh set of primaries and secondaries indicates this is either a juvenile Monteiro’s Storm-petrel or an early adult Grant’s Storm-petrel. Such birds cannot be identified with certainty on current knowledge, and despite perceived structural differences such as the less notched tail and sturdier overall appearance for Grant’s Storm-petrel, a bird such as this is best left unidentified.

‘band-rumped storm-petrel’ off Graciosa, early August 2012 (Vincent Legrand). The fresh set of primaries and secondaries indicates this is either a juvenile Monteiro’s Storm-petrel or an early adult Grant’s Storm-petrel. Such birds cannot be identified with certainty on current knowledge, and despite perceived structural differences such as the less notched tail and sturdier overall appearance for Grant’s Storm-petrel, a bird such as this is best left unidentified.

‘band-rumped storm-petrel’ off Graciosa, early August 2012 (Vincent Legrand). Grant’s Storm-petrels are on average more square-tailed than Monteiro’s Storm-petrel. However, Flood and Fisher (2011) advise to exercise extreme caution as there is much overlap in this feature between taxa. This problem is accentuated in judging these features in field conditions by apparent variation caused by angle of view and posture of bird which is further complicated in varying weather conditions. The shape of the tail is best assessed on square-on photographs and the presence of a deep fork is a stronger feature than an apparent square ended tail, which could be a result of feathers being splayed.

‘band-rumped storm-petrel’ off Graciosa, early August 2012 (Vincent Legrand). Grant’s Storm-petrels are on average more square-tailed than Monteiro’s Storm-petrel. However, Flood and Fisher (2011) advise to exercise extreme caution as there is much overlap in this feature between taxa. This problem is accentuated in judging these features in field conditions by apparent variation caused by angle of view and posture of bird which is further complicated in varying weather conditions. The shape of the tail is best assessed on square-on photographs and the presence of a deep fork is a stronger feature than an apparent square ended tail, which could be a result of feathers being splayed.

Adult Monteiro’s Storm-petrel, August 2012 (Vincent Legrand). Other summer breeding ‘band-rumped storm-petrels’ from Madeira and Cape Verde would also be moulting inner primaries during the late summer, and as such, these birds would be ‘impossible’ in some cases to tell from Monteiro’s Storm-petrel. A Madeiran Storm-petrel was actually sound recorded from within the Monteiro’s colony on Graciosa in May 2007 (Robb et al 2008) so this potential identification hazard is proven. Monteiro’s Storm-petrel is not called a ‘cryptic species’ for no reason!

Adult Monteiro’s Storm-petrel, August 2012 (Vincent Legrand). Other summer breeding ‘band-rumped storm-petrels’ from Madeira and Cape Verde would also be moulting inner primaries during the late summer, and as such, these birds would be ‘impossible’ in some cases to tell from Monteiro’s Storm-petrel. A Madeiran Storm-petrel was actually sound recorded from within the Monteiro’s colony on Graciosa in May 2007 (Robb et al 2008) so this potential identification hazard is proven. Monteiro’s Storm-petrel is not called a ‘cryptic species’ for no reason!

A further complication is other taxa of ‘band-rumped storm-petrels’, particularly first-summer from both the summer and winter breeding populations. The dispersal ranges of the various taxa of ‘band-rumps’ are not fully understood, immature or adult and birds from any population in principle could be present in Azorean waters at any time of year. This could lead to confusion in assigning taxa using moult timing. However, despite all the complications, a long-winged non-moulting bird with a deep forked tail in early summer and a similarly structured bird moulting its inner primaries in August/September in the core breeding range can, on balance, safely be considered a Monteiro’s Storm-petrel.

Hitting the jackpot?

We therefore concentrated pelagic efforts on the Bank of Fortune, coordinating three separate trips (with a total of twelve days at sea) in early August 2012, late August 2013 and early September 2013.   Unbelievably, as well as gaining excellent views of Monteiro’s Storm-petrel, each of the three trips recorded a Swinhoe’s Storm-petrel!

Even more outstanding was our discovery of a Zino’s Petrel on the bank in 2011 (which was identified by Bob Flood). This is one of few sight records of this species away from its breeding area, and confirms geolocator studies which show that the species disperses into Azorean waters.

Geolocator studies also incredibly show that Bermuda Petrels regularly disperse into Azorean waters and we hope to connect with one in the future. Bermuda Petrel has already been recorded on the Azores – an individual was famously captured and re-captured in a burrow on several occasions between 2002 and 2006 on Santa Maria.

Further trips were arranged in 2014, 2015 and 2016 confirming the reliability of the Bank of Fortune for Monteiro’s and Swinhoe’s Petrel, with Swinhoe’s recorded on all six trips since 2012. The Bank also held more surprises with Brown Booby in 2013, South Polar Skua in 2014, Fea’s Petrels in  2013 and 2016 and Sooty Terns (a breeding pair on Praia islet) were encountered most years.

The following table shows our pelagic sightings to date, though as more birders and pelagic trips focus on the Bank of Fortune and beyond we’re hopeful of some more significant records. Bob Flood and Ashley Fisher have identified the Azores as ‘The northeast Atlantic Pterodroma hotspot’ based on past records and geolocator studies. So with Zino’s and Fea’s Petrels already recorded, we’re holding our breath in the wait for a Bermuda, Black-capped or Trindade Petrel next…

Zino’s Petrel (Harro Müller). This record received a detailed discussion by Flood and Fisher 2013. Geolocator studies have revealed that birds disperse widely into the North Atlantic from their breeding grounds in Madeira.

Swinhoe’s Storm-petrel (Peter Alfrey). Remarkably, individuals of this species have been seen on each of the last three pelagic expeditions off Graciosa.

Swinhoe’s Storm-petrel (Peter Alfrey). Remarkably, individuals of this species have been seen on each of the last three pelagic expeditions off Graciosa.

Brown Booby off Graciosa, September 2013 (Peter Alfrey). The third record for the Azores.

Brown Booby off Graciosa, September 2013 (Peter Alfrey). The third record for the Azores.

Long-tailed Skua (Peter Alfrey)

Long-tailed Skua (Peter Alfrey)

Fea’s Petrel off Graciosa, September 2013 (Harro Müller)

Fea’s Petrel off Graciosa, September 2013 (Harro Müller)

Great Shearwater off Graciosa, August 2013 (Richard Bonser). Phenomenal views of this South Atlantic breeder can be had alongside the innumerable Cory’s Shearwaters.

Great Shearwater off Graciosa, August 2013 (Richard Bonser). Phenomenal views of this South Atlantic breeder can be had alongside the innumerable Cory’s Shearwaters.

Sooty Tern, Praia Islet off Graciosa, August 2013 (Richard Bonser). One of up to two adults that are regularly recorded in the tern colony on the island.

Sooty Tern, Praia Islet off Graciosa, August 2013 (Richard Bonser). One of up to two adults that are regularly recorded in the tern colony on the island.

South Polar Skua (Richard Bonser). One of the surprise highlights of the 2014 pelagic trip.

South Polar Skua (Richard Bonser). One of the surprise highlights of the 2014 pelagic trip.

Pelagic Trips from Graciosa 2011 to 2016 (Cumulative totals for trips each of 3.5 days at sea)

Species June 2011 August 2012 August 2013 September 2013 August 2014 August 2015 August/

September 2016

Fea’s Petrel       1     2 (fea’s-type)
Zino’s Petrel   1          
Bulwers Petrel 4 18 1 3 11 1 8
Cory’s Shearwater x X x X X X X
Great Shearwater     60+ 100+ 300+ X 130
Sooty Shearwater 5     20+ 7   21
Manx Shearwater 4 5 1 4 6    
Barolo’s Shearwater 3 1     1 1  
Wilson’s Storm Petrel 15 6 7 1 3 3 5
Swinhoe’s Petrel   1 1 1 1 1 1
Monteiro’s Petrel 50+ c20 C30 10+ 50 10+ 120+
‘Grant’s’ Petrel   c10 2+ 2+ 2+   X
Brown Booby       1      
Northern Gannet 1            
Grey Phalarope 1            
Pomarine Skua       1 1 1 1
Arctic Skua       5 3 1 5
Long-tailed Skua     1 3 3 1 2
Great Skua 4            
South Polar Skua         1    
‘Azores Gull’ X X X X X X X
Lesser Black-backed Gull   1 X X X X X
Sabine’s Gull         1    
Roseate Tern X X X 20+ X X X
Common Tern X X X X X X X
Arctic Tern         1    
Sooty Tern 1   1 2 3 1  

*A Solitary Sandpiper was also recorded at sea in August 2012.

*Trindade Petrel was recorded by an independent pelagic birder off Graciosa in 2012.

x- present throughout

Other Wildlife from Graciosa 2011 to 2016 (Cumulative totals for trips of 3.5 days at sea)

Species June 2011 August 2012 August 2013 September 2013 August

2014

August/

September 2016

Sperm Whale   4     1 2
Cuvier’s Beaked Whale 6         4
Northern Bottlenose Whale   1        
Sowerby’s Beaked Whale   1     5 4
Minke Whale   1        
Common Dolphin 200+ 100+ 100+ 100+ 10  
Bottlenose Dolphin 50+ 10+ 20+ 10+ 30+ x
Spotted Dolphin   50+ 20+ 50+ 20+  
Striped Dolphin           25
Risso’s Dolphin 12+ 20+        
Loggerhead Turtle 1 3 2 7    
Sunfish 1          
Blue Shark 3     3 1  
Hammerhead Shark   1        
Oceanic White-tip Shark       1    
Breaching Sowerby Beaked Whales (Richard Bonser). Regularly recorded on the pelagics.

Breaching Sowerby Beaked Whales (Richard Bonser). Regularly recorded on the pelagics.

 Common Dolphins (Gareth Knass)

Common Dolphins (Gareth Knass)

Spotted Dolphins (Vincent Legrand)

Spotted Dolphins (Vincent Legrand)

 Blue Shark with pilot fish (Harro Müller)

Blue Shark with pilot fish (Harro Müller)

Logistics

The best way to see Monteiro’s and Grant’s Storm-petrels, as well as other seabirds on the Azores, is to join an organised pelagic to the area with Peter and Richard in partnership with travel agents Azores Choice and Diving Graciosa. This year’s pelagic trip will run from 27th August to 1st September. So if you are interested in joining this trip (or subsequent trips) please email Peter at littleoakgroup@btinternet.com. This trip can also be combined with a trip to see the Azores Bullfinch, and it’s also likely that the first American waders of the autumn will be arriving in the famous Cabo da Praia quarry.

Acknowledgements

Many thanks to Bob Flood for improvements to the text of this article.

Thanks to all the birders that have participated in the pelagics. Special thanks and indebted to Ian from Azores Choice for sorting out all the logistics and of course to Rolando Oliveira and his crew from Diving Graciosa for taking us out to sea.

2011 Team

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