13/05/2011
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Jump-starting the spring in the Strait of Gibraltar, March–April 2011

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This spring I had an opportunity to kick-start the season whilst at the same time making sure I was home again for the peak period on my local patch. Needless to say I took the chance and headed south...

A four-week trip offshore in the Mediterranean and the Strait of Gibraltar provided plenty of migration interest. As this was work I chose the night shift, hoping to make the most of the dawn migration, but as it happened I had to wait for a couple of hours after shift before it became light enough to bird at around 08:00 — frustrating. An hour or two were spent birding on deck each day.

The first few days of the trip were spent between Spain and Ibiza, where there were generally few birds to be seen. Sightings here included a few Robins onboard, at least two of which were seen to leave the deck repeatedly and fly out over the sea apparently almost landing — though it is hard to say what they were actually trying to do. It is very rare to see passerines landing deliberately on the sea and taking off again, but it does happen.


Ringed Barn Swallow takes a break onboard off Ibiza.


Eurasian Robin thinking about landing on the sea.

A few Barn Swallows were seen, one of them ringed but just too far away to allow me to read the ring number. It would have been brilliant to know where this bird was ringed and to have reported it whilst it was actually on migration. A few each of Scopoli's and Balearic Shearwater were seen, and a Lesser Kestrel took a passerine off the helideck just west of Ibiza.


Illustrating the variation in Balearic Shearwater plumages.

Audouin's Gulls were typically most numerous around the vessel during the hours of darkness, usually clearing off shortly after dawn. This reinforces previous experiences with this species: it seems to be very much a nocturnal feeder that readily exploits the lights of the vessel to find prey. Yellow-legged Gulls joined them in this, but were usually in the minority.


Audouin's Gull — nice post-dawn view.


Audouin's Gull feeding beside the vessel — pictured here catching a small fish.


Audouin's Gull just as dawn breaks.

From a personal perspective, one of the best sightings wasn't a bird at all, but an Ocean Sunfish that came right up to the vessel before disappearing again.


Ocean Sunfish approaches the vessel.

By 24th March we had completed our work in the Mediterranean and moved to the western end of the Strait of Gibraltar, where the distance between Spain and Morocco was about 45km. We were met by storm-force winds of 60–70 knots; amazingly, there were still birds moving even under such horrendous conditions. It was barely possible to stand still on deck, even in relative shelter, yet Kestrel, Mediterranean Gulls and more were seen.

On the 25th March the wind eased to between 30 and 40 knots; this seemed to trigger a huge movement of Scopoli's Shearwaters, with at least 1000 passing in a few hours. Many of these could be identified by the extent of white on the underside of the primaries. However, some birds more closely resembled Cory's Shearwater, with dark primaries and a "messy" leading edge to the hand.

As on a number of previous occasions, the shearwaters were more visible closer to shore; relatively few birds were seen passing "out in the middle". I am unsure whether this is because the birds follow the coast as a leading line, making use of lower wind speeds, or because there is more life in the shallower water nearer the coasts.

This was the last day during the trip that Mediterranean Gulls were seen. Other seabirds noted were Great Skuas and Gannets (both species seen on a number of dates).


Scopoli's Shearwater (looking dark-faced — not what it says in the Advanced Bird ID guide but this may be due to lighting).


Scopoli's Shearwater.


Cory's Shearwater.

The strong easterly winds did not seem to deter migrating raptors unduly: at least 12 Marsh Harriers and a probable Montagu's somehow made the crossing and headed inland — right into a windmill "farm". It's amazing that planning permission can be given to build windmills in such places....

Flocks of small passerines, mostly finches, also passed, but were incredibly difficult to identify as both the birds and the observer were buffeted by the strong winds. At least some of these birds were Goldfinches.


Windmills greeting migrating raptors after the sea crossing.


Migrating female Marsh Harrier.

Although the days settled into something of a routine, something unexpected often turned up — and the opposite also occurred. On 28th March conditions were significantly calmer and expectations were therefore high. Disappointingly no raptors at all passed — but the first bird was a Roller, which circled the vessel before continuing. A few each of Spoonbill and Cattle Egret made up for the lack of birds of prey. Presumably the raptors were less affected by wind drift in the better conditions and crossed further east where the sea crossing is shorter.

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Migrating Roller.


Migrating Spoonbills.


Migrating Cattle Egret.

On 1st April winds were again very strong, in excess of 40 knots from the east. Incredibly, there was quite a bit of migration despite the howling gale with wind whipping up spray. It was largely strong fliers such as Swifts and hirundines that were on the move. Highlights were a few flocks of Bee-eaters numbering around 100 in total, and a male Montagu's Harrier blown past at high speed. Other species included Cattle Egrets, a few Marsh Harriers and several Kestrels. Again many passerine flocks went unidentified. Standing on deck being buffeted by the gale with constant noise from the wind, sea and the vessel meant this was no relaxing experience.



Part of a flock of Bee-eaters.


A male Montagu's Harrier gets blown past.


A Marsh Harrier struggles in the wind.

Dawn on 2nd April was rather calmer, and again the migration was disappointing. Small numbers of Scopoli's Shearwaters and a single Balearic passed. Surprise birds were a House Sparrow calling from the helideck — this surely must have been blown from somewhere rather than being on actual migration — and a flock of Flamingos. Audouin's Gulls continued to turn up during the hours of darkness.



A flock of Flamingos make the crossing.

The next day was the calmest experienced. Close to the Moroccan coast the vessel was inundated with moths during the night. Many species were present, among them Silver Y and Striped Hawk-moth. Yet again there were indications that Scopoli's Shearwaters keep closer to the coast, with over 40 seen heading into the Mediterranean. Other bird species included Great Skua, Yellow Wagtail and Bee-eater — the latter feeding on moths from the vessel. As I left the deck to go to my cabin a huge grasshopper turned up: a fantastic-looking creature!


Insects migrate too!


Bee-eater.


Grammodes bifasciata, one of several species of moth onboard.

Monday 4th April was calm and there was little to be seen; on the 5th winds in excess of 45 knots were experienced and again little passed, just a Kestrel and a couple of Swallows.

The following day was much better, despite a 35-knot easterly. First (and best!) bird to be seen in the half-light was a Gull-billed Tern. Cattle Egrets, a couple of Little Egrets, Marsh Harriers, a big movement of hirundines, several Yellow Wagtails, a few Tree Pipits, 80+ Goldfinches and lots of unidentified passerines battled their way north.


Northbound female Marsh Harrier.

Strong easterly winds dominated once again on 8th April with wind speeds in excess of 45 knots. The routine dawn vigil produced a Turtle Dove, two Cattle Egrets, a few Scopoli's Shearwaters and a male Montagu's Harrier as highlights. The wind abated somewhat in the evening and a steady passage of hirundines was observed, along with Kestrels, Sparrowhawks, Marsh and Montagu's Harriers. Knowing that this passage was happening did not make having to work any easier....

Calm conditions on 9th April resulted in a "fall" of at least 26 Striped Hawk-moths, but very few other moth species were involved this time. It was rather quiet birdwise, but a flock of 32 Greater Flamingos, several Yellow Wagtails and at least 10 presumed Scopoli's Shearwaters passed. The best sighting was a large Basking Shark that passed quite close to the vessel just after dawn.


Migrating Greater Flamingos.


Basking Shark.


Striped Hawk-moth (Julian Bell).

The last day in the Strait of Gibraltar was again calm and there was little to be seen, although a new species for the trip, a Song Thrush, was scared down to deck by a passing Montagu's Harrier.


The last Montagu's harrier of the trip.

This was not quite the end of the birding, though: fields full of Red-rumped Swallows and a roadside Stork's nest were seen from the taxi that drove us from the port at Cadiz to the airport on the way home to much less spring-like conditions in Norway.

Written by: Julian Bell