Spain’s three pelagic destinations operate on genuinely different calendars. The Gulf of Cádiz — where the Birding the Strait trips depart from Chipiona in Cádiz Province — runs a four-month season from July through October, centred on the post-breeding dispersal of the Critically Endangered Balearic Shearwater and the autumn trans-Atlantic skua migration. On the Atlantic coast, Galicia’s Cañón de Arousa Atlantic Pelagic out of O Grove runs across most of the year, peaking April through October. Further east, Cantabria’s Bay of Biscay Seabird Pelagic from Santoña covers a narrower mid-August to mid-November window as the same post-breeding seabirds funnel southwest along the region’s narrow continental shelf.
Getting the timing right matters for all three, and the choice between them depends heavily on which species you are prioritising and when you can travel.
Gulf of Cádiz: July to October
The Gulf of Cádiz pelagic season is anchored by one defining species: the Balearic Shearwater. With a global population estimated at fewer than 20,000 birds — all breeding exclusively on the Balearic Islands in the western Mediterranean — every individual passes through or near the Strait of Gibraltar during post-breeding dispersal from late June onwards. The shelf-break waters 15–18 nautical miles offshore from Chipiona are consistently documented as one of the most important post-breeding foraging areas for the species in the world. The Gulf of Cádiz Pelagic run by Birding the Strait reaches this shelf edge in approximately 2–2.5 hours, chumming with up to 40 kilograms of fish oil and offal throughout.
July
The season opens in July as the first Balearic Shearwaters arrive from the Mediterranean. Numbers build through the month; early July trips typically produce a few dozen individuals, late July trips regularly reach triple figures. Cory’s Shearwater is already numerous, Great Shearwater peaks from July into August, and Sooty Shearwater adds a third large shearwater species. Wilson’s Storm-Petrel is present from July, and the first Great Skua of the season appears in late July.
August: Peak Season for Shearwaters
August is the prime month for peak shearwater diversity and raw numbers. Balearic Shearwater concentrations are at their highest, with multiple hundreds of individuals on productive trips and counts into the thousands on optimal days. Storm-petrel diversity peaks in August and September, with Wilson’s and European Storm-Petrel both attending the chum slick. Pomarine Skua begins to appear in increasing numbers, and Sabine’s and Audouin’s Gull are both regular.
September: Peak Season for Skuas
September shifts the balance toward the autumn passage. Balearic Shearwater numbers remain high into mid-September, while all four North Atlantic skua species are now on the move: Great, Pomarine (peaking September–October), Arctic (August through October), and in smaller numbers Long-tailed. Sabine’s Gull is at its most numerous, and the first Leach’s Storm-Petrel of the season can appear.
October
October extends the season with a shift in composition. Balearic Shearwater numbers decline as birds continue south, but October is the best Gulf of Cádiz month for Long-tailed Skua, with Pomarine Skua passage intensifying and Grey Phalarope beginning to appear. The season ends in late October as shearwater passage dwindles.
Galicia: Year-Round, Peak April–October
Unlike the other two Spanish pelagics, the Cañón de Arousa Atlantic Pelagic from O Grove doesn’t run on a narrow migration window — trips are scheduled across most of the year, with peak season from April through October spanning spring migration, summer tubenose concentrations, and autumn dispersal.
Cory’s Shearwater is common April to October, when birds breeding on the Canary Islands and Azores forage north into Galician waters. Balearic Shearwater is regularly seen, with roosts of up to 1,500 birds recorded in La Lanzada bay near O Grove and two distinct peaks — April–June and September–October — rather than the single mid-summer peak seen further south. Sooty and Great Shearwater occur in autumn, Wilson’s Storm-Petrel is a regular summer and autumn visitor, and all four skua species pass through on autumn migration alongside Sabine’s Gull. Manx Shearwater is a year-round presence near the breeding colonies on the outer islands.
Cantabria: Mid-August to Mid-November
The Bay of Biscay Seabird Pelagic from Santoña runs a single, well-defined autumn window: mid-August through mid-November, timed to the southwestward post-breeding migration of seabirds dispersing from northern Atlantic and Arctic colonies along Cantabria’s unusually narrow continental shelf.
Balearic Shearwater is present from July through the full season, alongside Cory’s, Sooty, Great, and Manx Shearwaters. All four European skua species pass through in regular autumn migration, as do Sabine’s Gull, Grey Phalarope, and European Storm-Petrel.
Best Months by Target Species
| Species | Best Months | Location |
|---|---|---|
| Balearic Shearwater | Jul–Oct (Cádiz); Apr–Jun & Sep–Oct (Galicia); Jul–mid-Nov (Cantabria) | All three |
| Cory’s / Scopoli’s Shearwater | Jul–Oct | All three |
| Great Shearwater | Jul–Aug | Gulf of Cádiz, Cantabria |
| Sooty Shearwater | Jul–Sep | All three |
| Manx Shearwater | Year-round | Galicia, Cantabria |
| Wilson’s Storm-Petrel | Jul–Sep | All three |
| European Storm-Petrel | Aug–Oct | Gulf of Cádiz, Cantabria |
| Leach’s Storm-Petrel | Sep–Oct | Gulf of Cádiz |
| Great Skua | Aug–Oct | All three |
| Pomarine Skua | Sep–Oct | All three |
| Arctic Skua | Aug–Oct | All three |
| Long-tailed Skua | Oct | All three |
| Sabine’s Gull | Aug–Sep | All three |
| Grey Phalarope | Oct | Gulf of Cádiz, Cantabria |
| Audouin’s Gull | Jul–Oct | Gulf of Cádiz |
Quick Reference: Which Site, Which Month?
July: The Gulf of Cádiz season opens and Galicia is in full swing; Cantabria doesn’t start until mid-August.
August: All three are active. The Gulf of Cádiz delivers the highest Balearic Shearwater counts of the season, Cantabria’s season opens mid-month, and Galicia continues its April–October peak.
September: All three remain productive. Gulf of Cádiz reaches peak skua diversity, Galicia enters its second Balearic Shearwater peak, and Cantabria is in full autumn migration.
October: All three are still running. October is the best month across the board for Long-tailed Skua and Grey Phalarope.
November: Only Cantabria’s Bay of Biscay trip is still active, into mid-month, and Galicia’s near-year-round schedule may still have dates on offer.
Can You Combine Them?
August–September is the window when the Gulf of Cádiz and Cantabria are both at or near peak simultaneously, with Galicia productive throughout. A combined itinerary could run Chipiona in early August, then travel north for a Cantabria departure in September, or add Galicia’s Cañón de Arousa trip at either end given its far more flexible schedule.
Practical Notes
Gulf of Cádiz access: Jerez de la Frontera Airport (XRY) is the closest airport to Chipiona, with connections from Madrid, Barcelona, and several European cities. Seville Airport (SVQ) is the primary international hub for Andalucía.
Galicia access: Santiago de Compostela Airport is closest to O Grove, with connections from Madrid and Barcelona plus a handful of European routes.
Cantabria access: Santander and Bilbao Airports both serve Santoña, roughly 45 minutes to an hour away by road.
Booking lead times: Gulf of Cádiz trips are announced via the Birding the Strait newsletter at the start of each season — the minimum six-participant threshold means early registration affects whether a trip runs. The Cañón de Arousa trip requires a 50% deposit before the Tuesday prior to departure. Aves Cantábricas trips in Cantabria are capped at 10 participants — contact the operator directly for scheduled dates.
Seasickness: The Gulf of Cádiz shelf-break crossing is generally manageable, but the shelf edge can be rough in southwesterly conditions. Both the Galicia and Cantabria trips reach genuinely open Atlantic water — come prepared with your preventive method of choice, taken well before departure.
For the full guide to which trips are available and what to expect on each, see our Best Pelagic Birding Trips in Spain. Browse all listed Spain pelagic trips at the Spain directory.