title: Evidence against observational spatial memory for cache locations of conspecifics in marsh titsPoecile palustris.
abstract: Many species in the family Paridae, such as marsh titsPoecile palustris, are large-scale scatter hoarders of food that make cryptic caches and disperse these in large year-round territories. The perhaps most well-known species in the family, the great titParus major, does not store food itself but is skilled in stealing caches from the other species. We have previously demonstrated that great tits are able to memorise positions of caches they have observed marsh tits make and later return and steal the food. As great tits are explorative in nature and unusually good learners, it is possible that such "memorisation of caches from a distance" is a unique ability of theirs. The other possibility is that this ability is general in the parid family. Here, we tested marsh tits in the same experimental set-up as where we previously have tested great tits. We allowed caged marsh tits to observe a caching conspecific in a specially designed indoor arena. After a retention interval of 1 or 24 h, we allowed the observer to enter the arena and search for the caches. The marsh tits showed no evidence of such observational memorization ability, and we believe that such ability is more useful for a non-hoarding species. Why should a marsh tit that memorises hundreds of their own caches in the field bother with the difficult task of memorising other individuals' caches? We argue that the close-up memorisation procedure that marsh tits use at their own caches may be a different type of observational learning than memorisation of caches made by others. For example, the latter must be done from a distance and hence may require the ability to adopt an allocentric perspective, i.e. the ability to visualise the cache from the hoarder's perspective.
  
  
  CONCLUSIONS
  Members of the Paridae family are known to possess foraging techniques that are cognitively advanced. Previously, we have demonstrated that a non-hoarding parid species, the great titP. major, is able to memorise positions of caches that they have observed marsh titsP. palustrismake. However, it is unknown whether this cognitively advanced foraging strategy is unique to great tits or if it occurs also in other parids. Here, we demonstrated that "pilfering by observational memorization strategy" is not a general strategy in parids. We believe that such ability is important for a non-hoarding species such as the great tit and, most likely, birds owning many caches do not need this foraging strategy.
authors.affiliation: Department of Biology, Lund University, Ecology Building, S-223 62 Lund, Sweden.
authors.forename: A Utku
authors.initials: AU
authors.lastname: Urhan
authors.affiliation: Department of Biology, Lund University, Ecology Building, S-223 62 Lund, Sweden.
authors.forename: Ellen
authors.initials: E
authors.lastname: Emilsson
authors.affiliation: Department of Biology, Lund University, Ecology Building, S-223 62 Lund, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Brodin
keywords: Cache pilfering; Food hoarding; Observational learning; Paridae; Scatter hoarding; Spatial memory