Evidence for search image in blackbirds (Turdus merula L.): short-term learning

A ‘search image’ is acquired as a result of a change in the ability of a predator to detect cryptic familiar prey. Blackbirds were presented with artificial prey dyed either to match the colour of the background (cryptic prey) or to contrast with the background (conspicuous prey). The results of experiment 1 provide some evidence that 10 wild blackbirds had more difficulty detecting cryptic prey than conspicuous prey. Detailed analysis of experiments 2 (11 wild blackbirds) and 3 (six captive blackbirds) revealed subtle changes in the reactions of the birds to cryptic prey. At first these birds were unable to detect cryptic prey, but subsequently improved their ability to detect such food. This short-term change is interpreted as evidence for search images.     

Foraging and territory utilization of blackbirds (Turdus merula) and song thrushes (Turdus philomelos)

Territory utilization of blackbirds and song thrushes is examined in relation to spatial and temporal changes in the distribution of prey. Pairs within a territory showed similar preferences for particular areas. There was considerable diurnal variation in foraging localities and overall the two species tended to concentrate their search effort in areas of high prey density. Rates of feeding attempts and feeding techniques also varied with time of day. Changes were similar in the two species. At high rates of feeding during the middle of the day the foraging range was more restricted than at other times. Over short time periods individuals searched non-randomly by avoiding recently exploited areas.     

乌鸫的繁殖行为与坐巢行为初步观察

于2009年3～7月、2010年3～6月,采用焦点动物观察法和全事件行为记录法对乌鸫(Turdusmerula)的孵卵及育雏行为进行了研究。结果表明,乌鸫是雌鸟孵卵,在孵卵期出现卵损失现象,具补卵行为;孵卵前期与后期的坐巢行为存在差异,且其坐巢时间、频次和坐巢率有随孵卵数递增的趋势。双亲育雏但以雌鸟为主,喂食模式3种:雌鸟喂食、雄鸟喂食、雄鸟将食物递给雌鸟由雌鸟喂食。随着雏鸟日龄的增长,喂食次数增多,暖雏行为减少,至育雏后期未观察到暖雏行为。为权衡孵卵期和育雏前期的能量分配,乌鸫在孵卵期及育雏前期分别采取时间长而频次少和时间短而频次多的坐巢策略。     

Influence de quelques procedures experimentales sur l'apprentissage discriminatif des formes visuelles chez le merle, Turdus merula (L.)

Contrary to an earlier work, this research demonstrates that blackbirds (Turdus merula) discriminate visual shapes (triangle—circle).Thirty-two blackbirds were tested in eight learning situations. Each experimental situation was defined by a different combination of the modalities of the three variables: (1)spatial contiguity of stimulus-response (F) or non-contiguity (F?); (2) use of the correction method of learning (C) or the non-correction method (NC) ; (3) use of procedure against lateralization (L) or its non-use (L?).Of the eight different learning situations, only three lead to discrimination learning of shapes by blackbirds, i.e. use of the NC method with either a procedure L, independent of the variables F or F?, or a variable F, independent of the procedures L or L?.The C method never leads to any discrimination of shapes, which explains the failure of an earlier worker who used this method.These results are interpreted in the framework of the theories of attention.     

Clumping versus spacing out: Experiments on nest predation in fieldfares (Turdus pilaris)

Fieldfares (Turdus pilaris), which nest solitarily as well as in colonies, offer an opportunity to assess within one species the relative advantages of clumping versus spacing out. An experiment with artificial, egg-baited nests showed that predation in the absence of fieldfares was higher on clumped than on scattered nests. In another experiment, we tested whether artificial nests run a higher risk of predation near solitary fieldfare pairs than near fieldfare colonies. Nest predation was higher near solitary fieldfare pairs than outside and inside fieldfare colonies. The risk probably was higher outside than inside colonies. Communal antipredator attacks is the likely cause of reduced predation near colonies. Even solitary fieldfare pairs confer some degree of protection, because predation was lower at artificial nests near solitary fieldfare pairs than at nests without neighbouring fieldfares.     

Social learning enhances search image acquisition in foraging brook trout

Brook trout feed primarily on prey items for which they have developed a search image. Periodically, fish are required to update their search images to match temporal variability in prey abundance. It is currently unknown how brook trout develop search images, but there is evidence to suggest that it could be influenced by social learning, wherein a fish learns a novel behavior through observation alone. Here we demonstrate that adult brook trout use social learning to quickly develop search images for novel prey. We trained a set of demonstrators to develop a search image for canned mealworms and subsequently moved demonstrators to treatment pools that contained naïve bystanders. We also had control pools that contained naïve bystanders and sham demonstrators that had not been trained on mealworms. Over an 8-day period, bystanders in treatment pools consumed 68 % of mealworms, compared to only 36 % in control pools. Moreover, social learning of search images was rapid as bystanders in treatment pools began feeding on mealworms in less than 1 day, whereas it took 7 days for bystanders in control pools to feed heavily on mealworms. Social learning of search images confers an adaptive advantage by reducing energetic costs of foraging.     

Evidence for trans-trans and cis-cis farnesyl pyrophosphate synthesis in Gossipium hirsutum

A protein fraction capable of catalysing the formation of all four geometrical isomers of farnesyl pyrophosphate has been isolated from cotton roots. Using neryl pyrophosphate and isopentenyl pyrophosphate as substrates the product was found to be cis-cis farnesyl pyrophosphate and possibly trans-cis farnesyl pyrophosphate. Geranyl pyrophosphate and isopentenyl pyrophosphate as substrates yielded trans-trans and possible cis-trans farnesyl pyrophosphate. During purification of the active protein fraction, the ratio of utilization of geranyl pyrophosphate and neryl pyrophosphate did not remain constant, indicating that two enzymes may be involved, one specific for cis C₁₀-substrate and the other for trans C₁₀-substrate.     

Acid invertase in germinating Lactuca sativa seeds: Evidence for de novo synthesis

Acid invertase activity in germinating lettuce seeds is first observed after 15 hr germination, from when it rises steadily at least till 30 hr of germination. The enzyme was purified about 500-fold using ammonium sulphate fractionation followed by isoelectric focussing. Labelling the enzyme with ³⁵SO₄ or leucine-¹⁴C during development of its activity, followed by purification suggests that acid invertase is synthesized de novo during germination. The possible significance of acid invertase in the metabolism of the seed is discussed.     

S-allele diversity in Prunus L. Cerasus subgenus from Iran

In this study, S-allele diversity of eight wild and two commercial species of the Cerasus subgenus in Iran was investigated using two primer pairs. A high level of S-allele polymorphism was detected among and within the species evaluated. Furthermore, most of wild species showed 2–4 alleles based on S-allele primers and may be considered as tetraploid. Sweet cherry cultivars, Siah-Mashhad, Siah-Shabestar, Takdaneh-Mashhad, Siah-Daneshkadeh and Protiva showed S₃S₁₂, S₃S₁₂, S₃S₁₂, S₃S₅ and S₃S₄ combinations, respectively, allele S₃ showing the highest frequency. Three Iranian sweet cherry cultivars had the same allelic combination (S₃S₁₂) that the same ancestor in genealogy of these cultivars may explain the loss of diversity observed at the S-locus. Wild cherry (mazzard) accessions showed wide range of alleles such as S₁, S₂, S₇, S₁₄ and S₂₀ and unknown alleles, while sour cherries showed S₆, S₉, S₁₃ and S₂₇ alleles. In conclusion, the conservation of these highly diverse native species of Iranian wild Cerasus germplasm is recommended for future breeding activity.     

Tests of search image and learning in the wild: Insights from sexual conflict in damselflies

Search image formation, a proximal mechanism to maintain genetic polymorphisms by negative frequency‐dependent selection, has rarely been tested under natural conditions. Females of many nonterritorial damselflies resemble either conspecific males or background vegetation. Mate‐searching males are assumed to form search images of the majority female type, sexually harassing it at rates higher than expected from its frequency, thus selectively favoring the less common morph. We tested this and how morph coloration and behavior influenced male perception and intersexual encounters by following marked Ischnura elegans and noting their reactions to conspecifics. Contrary to search image formation and associative learning hypotheses, although males encountered the minority, male‐like morph more often, sexual harassment and clutch size were similar for both morphs. Prior mating attempts or copula with morphs did not affect a male''s subsequent reaction to them; males rarely attempted matings with immature females or males. Females mated early in the day, reducing the opportunity for males to learn their identity beforehand. Once encountered, the male‐like morph was more readily noticed by males than the alternative morph, which once noticed was more likely to receive mating attempts. Flexible behavior gave morphs considerable control over their apparency to males, influencing intersexual encounters. Results suggested a more subtle proximal mechanism than male learning maintains these color polymorphisms and call for inferences of learning to be validated by behavior of wild receivers and their signalers.     

Floral biology of Echinopsis chiloensis ssp. chiloensis (Cactaceae): Evidence for a mixed pollination syndrome

In this study the flower biology of Echinopsis chiloensis ssp. chiloensis, a columnar cactus occurring in Central Chile, is investigated, in particular its pollination syndrome, its visitors, their frequencies and behaviors and their pollination efficiencies. As statements on floral anthesis of this species are contradictory, this study also intended to elucidate both its beginning and duration. A pollinator exclusion study of a total of 162 flowers from 12 plants was conducted at one of the two study sites. Fruit and seed production as well as seed viability were documented to evaluate pollinator efficiencies.     

Varied-mapping conjunction search: evidence for rule-based learning

Five experiments were carried out to examine whether top-down processes can aid search, even when targets and distractors are variably mapped. Experiments 1a and 1b determined that effortless VM search can be obtained in Contrast Polarity X Orientation and Color X Orientation conjunction search when one feature dimension remains consistently mapped across blocks. Experiment 2 showed that efficient VM search is possible when both dimensions are variably mapped. In Experiment 3, efficient VM search was found when target-distractor reversals occurred on a trial-wise basis. Experiments 4 and 5 found that VM search deteriorates when target identity is not known prior to display onset. These studies demonstrate the role of top-down mechanisms in the development of efficient VM search and present several challenges to strength-theoretic views on the mechanisms underlying automaticity.     

Toxoplasma gondii: Evidence for the transmission by semen in dogs

Ten male dogs were distributed into three experimental groups for infection with Toxoplasma gondii: GI - three dogs inoculated with 2.0 × 10⁵ P strais oocysts, GII - three dogs infected with 1.0 × 10⁶ RH strain tachyzoites, and GIII - four controls dogs. Several clinical parameters were evaluated. IFAT was performed to detect anti-T. gondii antibodies. Presence of the parasite in semen was evaluated by PCR and bioassay techniques. Tissue parasitism was examined using bioassays and immunohistochemistry in testicle and epididymis fragments collected after orchiectomy. In semen samples collected from these two groups, the presence of T. gondii was verified by bioassays and PCR. T. gondii was detected by immunohistochemistry in tissues (testicle and epididymis fragments) of all six experimentally infected dogs. The T. gondii-positive seminal samples were used in the artificial insemination (AI) of four female dogs free of toxoplasmic infection. Seven days after AI, all of the female dogs presented serologic conversion (IFAT). Fetal reabsorption occurred in two of the dogs, while the others sustained full-term gestation. Several T. gondii cysts were detected in the brains of four offspring. These results suggest that T. gondii can be sexually transmitted in domestic dogs.