We spent a morning at RSBP Titchwell – 21 October, 2010. Walking back from the beach along the embankment at about 12:00 we stopped to watch a Black-tailed Godwit (Limosa limosa) feeding in the brackish marsh close to the embankment. Soon after we turned our attention to a small group of ducks. Measured on Google Earth they were around seventy metres distant on a mudbank opposite the north bund of the brackish marsh. The group consisted of 2 Mallard (Anas platyrhynchos), 15 Teal (Anas crecca) and 8 Wigeon (Anas penelope). We watched for about half an hour during which time they were constanly running/waddling (more often running than waddling, giving an overwhelming impression of urgency - and on the return journey also) to the water's edge, which was approximately 2 metres from the vegetation. They were apparently drinking and returning back up onto banking and into the vegetation where they continued feeding. Unfortunately the vegetation in which they were feeding was too long to be able to discern what was being eaten. They, all three species, spent roughly 20-30 seconds feeding before returning to the water where they spent a similar length of time during which they appeared only to drink. I posted details of the behaviour on the RSPB Titchwell blog asking if anyone had come across this behaviour and a member of staff suggested that they may have been feeding on Purple Glasswort (Salicornia ramosissima) and that they were trying to interpret the behaviour.
Checking BWPi for food items taken by these species and their feeding methods confirms that all these species have been recorded eating Salicornia sp, including seeds, at this time of year. Other plant species may, of course, have been involved. However, although both Mallard and Wigeon are noted as adopting grazing as a feeding method for Teal grazing is not mentioned. Rather, Teal, and Mallard, is noted as, among other methods, picking items off the surface of water or vegetation. There is, however, no mention of this particular combination of grazing/picking from the surface combined with what appeared to be drinking. It could not be determined whether or not the birds were feeding on vegetative matter and/or seeds so it was not possible to be clear as to whether or not they were grazing, in the general sense of the word, or whether they were picking seeds from the plants or both. Beyond that it would be interesting to know why such regular, and presumably, fairly copious amounts of brackish water were required – assuming that the birds were really drinking. Or were they washing food items?
Would be grateful if anyone could shed any light.