Border incidents: land birds and marine animals
I am a marine biologist and have for many years been specially interested in intertidal animals, of course mostly my beloved amphipods. Just this year we published a survey of the Norwegian Gammaridae, the most common group of shore amphipods. I have also my whole life been interested in birds and their behaviour, and I have in this way regularly come across cases where land birds somewhat unexpectedly foraged on the shore. I use here a division of our birds in seabirds, shore birds and land birds, which I probably think is mostly self-explanatory. Not quite, though: there are a number of ‘land birds’ that have specialized in such a way, that they easily could have been called shore birds. I watched the ‘tussac birds’ (and also Cobb’s Wren) on the shores of the Falkland Islands, and other Cinclodes species (topically called Seaside and Surf Cinclodes) on the rocky shores of Peru and Chile, and they are confined to the coast and foraged almost exclusively intertidally. On the Galapagos Islands the local Yellow Warblers often foraged in the intertidal, but I don’t know what their prey was. The closest thing that we have here in Europe are the Rock Pipits, but although strictly coastal in distribution, to my eyes they are still much less confined to the actual shores.
White Wagtails are often found on the shore, but I think they still mostly chase insects there—we have a number of coastal midges, with intertidal larvae, up here, and there are lots of flies on wrack.
A bird that here north forages a lot in the intertidal and clearly feeds on marine animals is our Hooded Crow. (In that respect it acts quite differently from the Carrion Crow I know from my younger years in the Netherlands. Even there the steadily dwindling numbers of wintering Hooded Crows there more often than not could be found on the shore). Here at the airport in Tromsø there is a smallish mudflat, dotted with large, algae-overgrown stones, which always hide a largish number of gammarid amphipods. The crows walk from stone to stone (one can easily track the footprints) and clearly hunt the amphipods. They also often forage on stony shores, but I am unsure whether they also there mainly chase amphipods and other crustaceans, or also feed on periwinkles and other mollusks. Of course they also scavenge here as elsewhere
The other regular bird crosser is the Common Starling, a bird that I know is heartily hated by many birders abroad, but greatly valued here as a harbinger of spring, so much so that we put out nest boxes to battle the steady diminishing numbers in our area. My first experiences with ‘shore starlings’ were from Holland, on Vlieland, one of the Wadden islands, where during my student years we had regular summer camps studying ‘Shorebirds and bottom fauna’, and where I was the bottom fauna man. One of my tasks was to ‘read’ the tracks made by the various bottom living invertebrates, and one of the tracks was a hole with a scribbly star of tracks around, made by the worm Nereis. I learned to recognize those everywhere, usually high up on the mudflats, and then discovered to my surprise that the local starlings also knew these tracks, walked from one to the next and tried to extract the fat worms. In the harbour of Den Helder I watched Starlings fetching shrimps from a shrimp boat and feed them to their young, and I also have seen, both In the Netherlands and in Norway, that Starlings fly like clumsy helicopters over the surface of the sea, and catch floating small dead fish. In Norway I see starlings often in the intertidal, where I think they may feed on gammarid amphipods. In one case, in the inner Sognefjord in W. Norway they were clearly so much habituated to this source of food, that in the few hours that high water rendered these prey items inaccessible, the Starlings rested in a row on the telephone wires, thus living in a similar tidal rhythm as many shorebirds. A few starlings try to winter in N. Norway, on the outermost islands, and they are almost wholly dependent on the shores.
In Norway we have a proverb: "I tider av nød spiser fanden fluer", which translates roughly as: in the hour of need the devil eats flies. Such hours of need occur here north now and then in late spring, when the migrant songbirds have returned and a sudden heavy snowfall makes much of their usual food inaccessible. On such days one can find many Fieldfares, Redwings, Bluethroats and even House Sparrows and Bramblings on the shore, feeding on what they can get. There may be seeds along the highwater-line—I often see the Snow Buntings, that are here in large flocks on spring migration, feed there, but I believe that the thrushes and chats mainly search for animal prey. Our most numerous bird, the Willow Warbler, does not frequent the sea shore at all, but I have on snowy and cold days seen them ‘helicoptering’ over freshwater, picking up mosquito larvae.
I am between cataract operations, and once more mostly house bound. I hope this is some interest and shall be very grateful for further examples of such border incidents.
Wim Vader, Tromsø, Norway
