Some info I came across:
"Multiple modes of sexual selection on a male trait. Courting males of about 17 species of fiddler crabs build sand or mud structures at the opening of their burrows to which they attract females for mating. Through direct observation and field experiments we are studying three causes of sexual selection of structure building in Uca beebei and Uca musica: 1) the differential attractiveness of structures, compared to unadorned burrow openings, to mate-sampling females, 2) the differential utility of structures as visual guideposts that males use to find their own burrows when courtship has produced errors in their non-visual orientation mechanism, which is based on path integration, 3) the differential effects of structures on the rate males detect, encounter and court females. Ultimately we hope to parse and measure the effects of each mode of sexual selection on structure building and design. Selection of mating preferences. We have shown experimentally that structures build by male fiddler crabs attract mate sampling females. Such preferences usually are thought to arise and be maintained by selection that is a consequence of mating males with the preferred trait. In this case, however, our studies strongly suggest that structures co-opt for mate choice a response that is selected by predation. Through field experiments we have shown that structures are attractive to males and females of species who don't build them, that females of structure building species do not prefer the structures built by males of their own species and that natural objects such a stones, shells and bits of wood are as attractive or more attractive than are male-built structures. Together the evidence indicates that male built structures elicit landmark orientation, the tendency of fiddler crabs to move toward and hide behind objects when they are at risk moving on the surface away from burrows, as are mate sampling females. Females who approach structures may benefit directly by reducing their mate search costs. We have shown that structure building is a condition-dependent trait suggesting that females may also benefit indirectly by mating structure builders. However such possible indirect benefits appear to be a fortuitous effect, rather than a cause of the evolution of the differential response to structures.