11th- 15th April: The Hascombe Gap and the Shalford Split

Following the excitement of last Sunday, things have gone back to a more gentle pace, with spring still fairly slow to arrive. On the 11th, no fewer than 3 Garden Warblers across the site represented a year tick, coming a day later than the first of 2016. A singing Willow Warbler (2 more today, at New Barn) was part of 61 species that day, but as I write this I still haven't seen either Martins, Wheatear, Cuckoo or Whitethroat. All of these I expect to record in the coming days and weeks, but a flyover Yellow Wagtail this morning was quite a surprise. Normally just 1 or 2 records a year, and almost exclusively in autumn, an early vis-mig session was rewarded today as an individual flew NNE over the Ridge, calling, at 06:48. In fact, despite the continued northerly wind, the first 40 minutes or so were decent, with 5 Swallows, 2 Linnets and a single Meadow Pipit heading north, and 5 Cormorants and an adult Lesser Black-backed Gull east.

2 more Gull species (Black-headed and Herring) were noted elsewhere throughout the morning, the first for a while. It was a Great Black-backed Gull on Thursday that got me thinking, and prompted me to get my maps out, resulting in this post. An adult (the 3rd record of the year) drifted over Scotsland Brook, quite out of place, at around 16:35. It soon struck me - within about a half kilometre from here to the west, I had seen Kittiwake, Great Black-backed Gull and 2 Cattle Egrets, all flying north, in the last 3 weeks. There surely had to be some reason behind this remarkable run, and below is a possible theory I have come up with.

The Hascombe Gap

Hascombe Gap map

The River Arun joins the English Channel at Littlehampton, and if one follows it north, it passes through such birding hotspots as Arundel WWT, Pulborough Brooks (where the river splits) and Climping Gap. At Loxwood, it splits. The Arun continues east, towards Horsham, and the Wey & Arun Canal goes north and west towards Surrey. Near Dunsfold, there is another, smaller split. The Wey & Arun Canal continues north and east, skirting the east of my patch near Cranleigh, eventually joining with the Wey at Shalford. To the north and west, a series of unnamed tributaries run for a short distance before they all stop around Loxhill, just before Hascombe.

The gap just beyond this collective stop, between Loxhill and Hascombe, is where the aforementioned sightings have come from. It seems possible that any birds following the Arun from the coast (should they not deviate at Pulborough/Loxwood) will find themselves here, at the end of the thinning streams, and will perhaps drop down to reorientate. It takes some favourable decision making, and maybe is a little ambitious, but it's just about possible. On a larger level, the gap extends from Loxhill in the west to Smithbrook/Rowly in the east, where the Wey & Arun canal is found continuing north, so this whole area could turn up something. Given the gap is most likely to effect birds moving up, spring is likely the best season for wayward bits and pieces.

It would seem any bird that has ended up here, should it wish to carry on following water, would have little choice but to continue north, through and just past the top of the patch, where the Wey & Arun meets the Wey at Shalford. The Thorncombe valley provides a natural funnel for this short journey, and would go someway to explaining the occurrence of species like White-fronted & Brent Goose, (presumed) Bewick's Swan, Curlew, Black-tailed Godwit, Whimbrel and a plethora of Raptors and Passerines all heading north/south over the last few years.

On the contrary, birds turn up at any place, and at any time, and maybe it's all just freak fortune!

The Shalford Split

Shalford Split map

This flyway theory was raised many years ago by Unstead Sewage Farm regulars. The river splits at Shalford, with the Wey & Arun Canal going south and west, and the Wey east. Unstead sits directly to the south of this split, with my patch a little further down. In theory this is two flyways meeting, and there is much evidence of birds using them and switching between the two in the last few decades.

Long-tailed Skua, a host of Gulls (including Sabine's and a flock of c.60 Kittiwakes), and a myriad of Waders/Raptors/Herons etc have all been recorded at Unstead. I am likely to miss any birds that are successfully following either river, perhaps being a bit far south of the split, but anything reorientating could/has passed over.

This, also, could be pie in the sky. Some theories suggest flyways don't really exist. Perhaps this is all overthought. Personally, I think there could be some logic behind it, and I will certainly be keeping it all in mind during the coming weeks.