Management of fat reserves and food caches in tufted titmice (Parus bicolor) in relation to unpredictable food supply

In the temperate zone, permanent-resident birds and mammalsthat do not hibernate must survive harsh winter conditions oflow ambient temperature, long nights, and reduced food levels.To understand the energy management strategy of food-hoardingbirds, it has been hypothesized that such birds respond to increasedstarvation risk by increasing the number of their hoards ratherthan by increasing their fat reserves and that they cache earlyin the day and retrieve their caches later to achieve fat reservesnecessary to survive the night We tested these hypotheses byobserving the responses in captivity of a caching bird, thetufted titmouse (Parus bicolor), to the combined influencesof reduced predictability of food and naturally occurring ambienttemperature and photoperiod. When the food supply was unpredictable,birds significantly increased both internal fat reserves atdusk and external food caches. Initially leaner birds tendedto increase their fat reserves to a greater extent and initiallyfatter birds tended to cache more food and to fly significantlyless. Half the birds also increased their dawn and mean dailybody mass. All birds tended to forage, gain body mass, and cachefood at significantly lower rates in the morning and at significantlyhigher rates in the evening. Cache retrieval showed the oppositetrend, with birds retrieving most of their caches in the morning.Our results do not support the hypothesis that caching birdsincrease caching rate but not body mass under an unpredictablefood regime. Instead fat reserves and food caches are both importantcomplementary sources of energy in food-hoarding birds. Energymanagement by wintering birds occurs in response to a numberof biotic and abiotic factors acting simultaneously; thus futuremodels must incorporate independent variables in addition tothe state of the food supply and time of day     

Spatial memory in a food storing corvid

This work suggests how food storing corvids use spatial memory to relocate caches, and how they can do this after some landmarks surrounding caches have become hidden due to leaf fall, snow fall or plant growth. Experiments involved training European jays (Garrulus glandarius) to find buried food, the location of which was specified by an array of 12 landmarks. Tests were then performed with the array rotated, or with certain landmarks removed from the array. The main findings were: (1) birds primarily remembered the position of the goal using the near tall landmarks (15–30 cm from the goal and 20 cm high); (2) birds obtained a sense of direction both from the landmark array and something external to the array; (3) birds did not use smell or marks in the surface of the ground to find the goal. Memory of near tall landmarks is likely to be functional for these birds since (a) nearer landmarks provide a more accurate fix, and (b) taller landmarks are less likely to be completely obscured by snow fall, leaf fall or intervening vegetation. The work also demonstrates the use of G.I.S. software for the analysis and representation of animal search patterns.     

Strategies of spatial learning for food storing in scrub jays

Western scrub jays (Aphelocoma californica) hide food and rely on spatial memory to recover their caches at a later date. To do this cache-and-recovery, they can use both spatial and site-specific cues. I examined these cues in an experimental setting. The experiment established that scrub jays, like other food storers, prefer to rely on the location of the caching tray rather than tray-specific cues. They could modify their preference for spatial cues through training in which spatial cues were made irrelevant. Even after such training, the spatial cues controlled the jays behaviour when the spatial and site-specific cues gave competitive information about the cached sites. Thus, the global spatial cues have priority but the jays use the local site-specific cues when the spatial cues do not give enough information about the cached site.     

Seasonal patterns of food storing in the Jay Garrulus glandarius

This study investigated seasonal patterns in food consumption and food storage in six captive Jays Garrulus glandarius. In the first experiment, seasonal changes in food-storing intensity were tested by presenting acorns (oak seeds, Quercus spp.) in spring, summer and autumn. There were no significant differences between the seasons in the amount of food eaten. However, significantly more food was taken and stored in the autumn than in the spring and summer months. In the spring and summer, the acorns were stored between the doorframes, on the ledges of the aviaries and under the bark of branches. In the autumn, Jays also began to hoard underneath the plastic sheeting covering the hard-board flooring by ripping the polythene to create a hidden cache site. The length of time over which the stored food was left before retrieval increased from summer to autumn. Food storing also occurred in spring and summer but was short term. The second experiment tested whether or not there were seasonal changes in food preference by presenting birds with acorns, peanuts and mealworms in the summer and autumn. More peanuts were eaten, taken and stored in the autumn than in the summer, and, as in the first experiment, significantly more acorns were taken and stored in the autumn. In the autumn, only a few mealworms were eaten before the birds stored acorns and peanuts, whereas in the summer, birds tended to eat most of the mealworms before they began to store. As in the first experiment, items tended to be buried in the ground in the autumn and left for longer periods before retrieval. These results are discussed in relation to the demand that each food type places on the Jay's time.     

Epidemiological typing of Bacillus spp. isolated from food.

Biotypes, fatty acid profiles, and restriction fragment length polymorphisms of a PCR product (PCR-RFLP of the cereolysin AB gene) were compared for 62 isolates of the Bacillus cereus group. Eleven isolates originated from various foods, and 51 isolates were obtained from pasteurized milk which had been processed by two different dairies. The isolates were clustered into 6 biotypes, 10 fatty acid groups, or 7 PCR-RFLP clusters. Isolates with mesophilic or psychrotrophic characteristics were preferentially distributed into specific fatty acid or PCR-RFLP groups (P = 0.004). Unique fatty acid clusters were predominantly found in milk samples of each dairy (P < 0.0001), suggesting that certain dairy plants may harbor plant-specific B. cereus which might constantly contribute to postpasteurization contamination.     

Transferable erythromycin resistance in Listeria spp. isolated from food.

An erythromycin-resistant (Emr) Listeria innocua and an Emr Listeria monocytogenes isolate both carried ermC genes, which code for rRNA methylases. The ermC genes were transferable by conjugation to recipient L. monocytogenes, Listeria ivanovii, and Enterococcus faecalis but did not appear to be associated with conjugative plasmids.     

Twelve-hour PCR-based method for detection of Salmonella spp. in food

A PCR-based method for the detection of Salmonella spp. in food was developed. The method, set up on typical salami from the Italian region of Marche, is sensitive and specific and shows excellent correlation with the conventional method of reference when naturally contaminated foods are analyzed. Moreover, it can be easily performed within a maximum of 12 h from food sampling, thus allowing prompt detection of Salmonella spp. in the food stocks analyzed.     

Detection of Salmonella spp. in food by a rapid PCR-hybridization procedure.

A rapid and sensitive PCR-hybridization procedure for detection of Salmonella serovars in food samples was developed. This method is based on three subsequent steps: (1) extraction of nucleic acids from a 2 ml aliquot of the pre-enrichment medium used for the conventional culture method after 6 h of incubation at 37 degrees C; (2) amplification with primers selected from the sequences of invE and invA genes; (3) Southern blot and hybridization with a biotin labeled oligonucleotide probe. The entire procedure requires 30 h. The PCR-hybridization assay was able to detect as little as 50 fg of purified chromosomal DNA of S. typhimurium and 0.2 cfu g-1 of an artificially contaminated food sample. Of 245 food samples analyzed by culture and PCR-hybridization, 20 were positive by both methods and 16 were positive by PCR-hybridization only. None of the 209 PCR-negative samples tested positive by culture. The sensitivity, specificity, alpha and beta error values of the results of the PCR-hybridization procedure, compared with those of culture, were 100, 92.9, 0 and 7.1%, respectively. These results indicate that a short pre-enrichment and PCR-hybridization could be used as a screening test for the detection of Salmonella in food samples.     

Mixed species flocking of tits (Parus spp.): a field experiment

Summary We tested two general models of flocking behaviour, namely the antipredation model and foraging efficiency model on mixed-species tit flocks (Parus spp.). After food addition the size of mixed-species flocks was significantly less than in the control samples. In the presence of extra food significantly more birds were observed either in monospecific flocks or solitary, than during the control observations. In the presence of a living predator the birds foraged in larger mixed-specifies flocks than during the control observations. In addition, the social behaviour of Great Spotted Woodpecker, Middle Spotted Woodpecker and Nuthatch shifted to mixed-specific flocking. The size of monospecific flocks was independent of both treatments. The density of birds increased significantly after food addition, while in the predator presence the birds tended to leave the forest. These results support the view that both the antipredation model and foraging efficiency model seem to be valid for mixed-species flocking. However, in the case of monospecific flocks, the territory maintenance could be the most important factor.     

Characteristic of Listeria spp. bacteria isolated from food products

The frequency of occurrance of Listeria strains in different food products was determined. Biochemical characteristic of the isolated strains was achieved in accordance with procedure included in PNEN ISO 11290 standard, genus was determined byApiListeria (bioMéieux) test. Sensitivity to selected antibacterial medicines was investigated using disck method and Mueller-Hinton 2 Agar medium. From the 577 examinated food samples 126 strains of Listeria were isolated and among them: 34.1% L. monocytogenes, 36,5% L. welshimeri, 19.0% L. innocua, 3.17% L. grayi, 0.79% L. seeligeri, 0.79% L. seeligeri/welshinmeri and 5.56% L. ivelshimeri/innocua. L. monocytogenes strains most often were found in minced pork, culinary products and in frozen vegetables. On the base of ApiListeria (bioMéieux) test the isolated L. monocytogenes strains were qualified into 2 biochemical types. It was found that all L. monocytogenes were sensitive to sulphametaksazol/trimetoprim and ampicyllin, 25% of strains were moderatety sensitive to penicillin and only 2 L. monocytogenes strains were resistant to gentamicin. Presence of Listeria spp. microorganisms in food products may be an production hygiene indicator for critical control point and show the possibility of contamination with L. monocytogenes strains.     

Seasonal metabolic acclimatization in mountain chickadees and juniper titmice

Mountain chickadees and juniper titmice from northern Utah were examined to determine metabolic and body-composition characteristics associated with seasonal acclimatization. These species use behavioral adaptations and nocturnal hypothermia, which reduce energetic costs. These adjustments could reduce the need for extensive metabolic adjustments typically found in small passerines that overwinter in cold regions. In addition, these species live at higher altitudes, which may also decrease metabolic acclimatization found in birds. Winter birds tolerated colder test temperatures than summer birds. This improved cold tolerance was associated with an increase in maximal thermogenic capacity or summit metabolism (M(sum)). Winter M(sum) exceeded summer M(sum) by 26.1% in chickadees and 16.2% in titmice. Basal metabolic rates (BMR) were also significantly higher in winter birds compared with summer birds. Pectoralis wet muscle mass increased 33.3% in chickadees and 24.1% in titmice in winter and paralleled the increased M(sum) and BMR. Dry mass of contour plumage increased in winter for both species and was associated with decreased thermal conductance in winter chickadees compared to summer chickadees. Chickadees and titmice show metabolic acclimatization similar to other temperate species.     

Physiological ecology of Mediterranean blue tits (Parus caeruleus L.): effects of ectoparasites (Protocalliphora spp.) and food abundance on metabolic capacity of nestlings

The consequences of nest ectoparasites, such as Protocalliphora larvae, on nestling birds have been the subject of numerous studies. Despite observed reductions in mass and hematocrit of chicks from parasitized nests, no studies have found any effect of Protocalliphora on nestling survival, suggesting that fitness consequences of Protocalliphora are either weak or occur after fledging. From experiments on the metabolic performance of chicks, we found that parasitized chicks suffer from reduced thermogenic and metabolic capacities as a result of decreased mass and hematocrit. Hence, Protocalliphora may potentially affect nestling survival after fledging, when energetically costly activities such as flight and moult are undertaken. Previous studies have demonstrated an increase in parental feeding rate to compensate for the detrimental consequences of parasite infestation. We tested whether parasite effects on nestling aerobic capacity were dependent on food availability during the feeding period. Measures of caterpillar densities and experimental manipulations of parasite loads allowed us to investigate relationships among host, parasite, and environment. A positive relationship between chick aerobic and thermogenic performances and caterpillar density suggests that negative effects of parasitism may be offset by increased food availability. This study provides the first measurement of the effects of an ectoparasite on metabolic competence in wild birds and documentation of the effect of food availability on ectoparasite virulence using a quantitative measure of food abundance.     

Energetic reserves of marsh tits (Parus palustris): food and fat storage in response to variable food supply

During the winter, small birds face the threat of starvationduring the day and overnight. The threat of starvation can bereduced by maintaining higher energetic reserves, either asinternal fat stores or as external hoards. I present here empiricaldata concerning the management of energetic reserves in responseto unpredictability in foraging success. Predictions of a modelwere tested using marsh tits (Parus palustris) experiencingconditions of low and high temporal variation in food supply.Under the high-variation treatment, birds increased externalhoards but not internal fat reserves. In addition, birds decreasedtheir mean hoard-recovery interval compared to conditions inwhich food was predictable. Detailed examination of body weightthroughout the day indicates that marsh tits delayed the accumulationof overnight fat reserves until relatively late in the day.Overall, these results support the theory that fat reservesare costly to acquire and maintain and suggest that marsh titsactively manage both internal and external energetic reserveswithin and among days.     

Antimicrobial activity of Pseudomonas spp. against food poisoning bacteria and moulds

M.H. LAINE, M.T. KARWOSKI, L.B. RAASKA AND T.-M. MATTILA-SANDHOLM. 1996. The present study demonstrates the siderophore production of two strains of Pseudomonas fluorescens and two of Ps. chlororaphis . The antimicrobial activities of these strains were studied against Salmonella typhimurium, Staphylococcus aureus, Fusarium culmorum, F. oxysporum and Aspergillus niger . Despite equal siderophore activities with various Pseudomonas spp. as measured by the chrome azurol S assay, the study shows how siderophore activity does not correlate with the antibacterial activity against food pathogens or with the antimould activity against pathogenic moulds. Furthermore, the results illustrate how siderophores are able to act both as growth inhibitors and stimulators.     

Surveillance and characterisation of Cronobacter spp. in Czech retail food and environmental samples

Cronobacter spp. (formerly Enterobacter sakazakii) are emerging, opportunistic pathogens that are linked with food-borne infections in neonates and infants. In the present study, 291 samples of food, 36 samples from a dairy farm and 140 samples of dust from vacuum cleaners were examined for the presence of Cronobacter spp. using chromogenic media and biochemical tests. Altogether, 72 Cronobacter spp. strains were isolated in accordance with the reference standard ?SN P ISO/TS 22964 (2006). No Cronobacter spp. strains were detected in 10 samples of infant milk formula or in samples from a dairy farm. Twelve out of 20 positive food samples were dry products. The incidence of Cronobacter spp. in instant and powdered products and spices (12 positive isolates out of 82 samples) was significantly higher than that in other foods (P?=?0.002), but lower than that in samples of dust (52 isolates; P?<?0.001). The incidence of Cronobacter spp. in dust from restaurants, bars and hotels (13 positive isolates in 20 samples) was significantly higher than that in dust from households (P?=?0.010). The polymerase chain reaction assay for the species-specific detection of the rpoB gene was performed in 49 isolates. Thirty-four Cronobacter spp. isolates were identified as Cronobacter sakazakii, nine isolates as Cronobacter malonaticus and one isolate as Cronobacter turicensis.     

Prey selection and foraging performance of breeding Great Tits Parus major in relation to food availability

We studied the nestling diet and the foraging performance of Great Tits in relation to prey abundance in the field. Numerous experimental studies present data on foraging decisions in captive Great Tits. Little is, however, known about prey selection in the field in relation to the food available and the consequences this has for the food delivery rate to nestlings. Since the foraging performance of the parents is one of the main determinants of fledging weight and juvenile survival, foraging behaviour is an important part of Great Tit reproduction. During the early breeding season up to 75% of the prey biomass delivered to the nestlings were spiders, which is in contrast with other studies. Only when caterpillars reached a size of 10–12 mg (approximately the average size of the spiders caught at that time) did the Great Tits change their preferences and 80–90% of the delivered prey masses were caterpillars, as reported by other authors. This 'switching' between prey occurred within a few days. It was not related to the changes in abundance but to size of caterpillars. The rate at which caterpillars were delivered to the nestlings (in mg/nestling/h) was strongly correlated with the caterpillar biomass available (in mg/m of branches) and nestling growth rate was significantly influenced by the mass of available caterpillars. The results provide evidence why perfect timing of breeding is so important for the Great Tit, and contribute to the understanding of the causal link between food supply, growth and breeding success.