Is the Starling Sturnus vulgaris a determinate layer?

European Starlings Sturnus vulgaris have been said to be determinate layers, that is, they do not react to egg removals by laying extra eggs nor to egg additions by laying fewer eggs. Especially in species with a relatively small clutch-size, such as the Starling, it is important to start these experiments early during the laying period to give the laying female the possibility of reacting to these additions and/or removals. I report here addition ( n = 11 nests) and removal experiments ( n = 35) early in laying period in a captive Starling colony. Additional information is presented about the development of incubation behaviour, a good predictor of clutch-size. When three eggs were added to nests at 1500h on the first day of laying, females laid the normal number of eggs, and incubation behaviour developed regularly. Egg removals (one egg on three successive days) that started early in the laying period (at 1500h on the first day or at 0800h on the second day) arrested the development of incubation behaviour and resulted in the laying of extra eggs. Removals later in the laying period had no effect on the number of eggs laid nor on incubation behaviour. Following Kennedy's (1991) terminology, the starling is an addition-determinate, and appears to be a removal-indeterminate, layer.     

Female Acheta domesticus track acoustical and visual targets with different walking modes

ABSTRACT. Female Acheta domesticus L. were tested for tracking model calling songs with different syllable periods on the Kramer treadmill in the dark, under homogenous light, and in the presence of a visually attractive target (black square) positioned either perpendicular to or in front of the invisible acoustical target. The females exhibited tracking of the two targets by different walking modes.     

How did this snail get here? Several dispersal vectors inferred for an aquatic invasive species

1. How species reach and persist in isolated habitats remains an open question in many cases, especially for rapidly spreading invasive species. This is particularly true for temporary freshwater ponds, which can be remote and may dry out annually, but may still harbour high biodiversity. Persistence in such habitats depends on recurrent colonisation or species survival capacity, and ponds therefore provide an ideal system to investigate dispersal and connectivity. 2. Here, we test the hypothesis that the wide distributions and invasive potential of aquatic snails is due to their ability to exploit several dispersal vectors in different landscapes. We explored the population structure of Physa acuta (recent synonyms: Haitia acuta, Physella acuta, Pulmonata: Gastropoda), an invasive aquatic snail originating from North America, but established in temporary ponds in Doñana National Park, southern Spain. In this area, snails face land barriers when attempting to colonise other suitable habitat. 3. Genetic analyses using six microsatellite loci from 271 snails in 21 sites indicated that (i) geographically and hydrologically isolated snail populations in the park were genetically similar to a large snail population in rice fields more than 15 km away; (ii) these isolated ponds showed an isolation‐by‐distance pattern. This pattern broke down, however, for those ponds visited frequently by large mammals such as cattle, deer and wild boar; (iii) snail populations were panmictic in flooded and hydrologically connected rice fields. 4. These results support the notion that aquatic snails disperse readily by direct water connections in the flooded rice fields, can be carried by waterbirds flying between the rice fields and the park and may disperse between ponds within the park by attaching to large mammals. 5. The potential for aquatic snails such as Physa acuta to exploit several dispersal vectors may contribute to their wide distribution on various continents and their success as invasive species. We suggest that the interaction between different dispersal vectors, their relation to specific habitats and consequences at different geographic scales should be considered both when attempting to control invasive freshwater species and when protecting endangered species.     

The effect of visual input on calling song attractiveness for female Acheta domesticus

ABSTRACT. Of twelve mature phonotactically-responsive female Acheta domesticus L., ten responded phonotactically to a wider range (30 or SO to 100 ms) of model calling song (CS) syllable periods (SP) on the Kramer treadmill in the dark than in a lighted visually structured arena (50–70 ms). When given a choice between the visually attractive target and the invisible loudspeaker, seven of the ten females that tracked a visually attractive target (black square) when presented alone in the light reduced the range of SPs they tracked phonotactically to 50–70 ms. Three of the ten females that were not strongly attracted to the visual target when presented alone, continued to respond to model calling songs with a wide range of SPs (30–100 ms) when given a choice between visual and acoustical targets under the same conditions. Two of the twelve females responded only to model calling songs with a 50–70 ms SP on the Kramer treadmill in the dark. These females did not change their choice for model calling song SPs when presented with the visually attractive target.