Effect Of Winter Temperatures Research Articles

Continental variation in relative hippocampal volume in birds: the phylogenetic extent of the effect and the potential role of winter temperatures

Hippocampal (HC) volume has been hypothesized to increase with an increase in food-hoarding specialization in corvids and parids. Recent studies revealed that (i) the HC/hoarding relationship is significant when a difference in HC volume between Eurasian and North American species is controlled for and (ii) the evolutionary association has been acting on a broader phylogenetic context involving avian families outside the Corvidae and Paridae. However, the phylogenetic extent of the continent effect has not been previously addressed. Using data representing 48 avian species, we performed a phylogenetic analysis to test if continental effects are important in a wider evolutionary spectrum. Our results support the observation that Eurasian species have generally larger HC than North American species if variation in food hoarding, which also varied between continents, was held constant. Surprisingly, the relationship between continental distribution and relative HC volume was significant when we included only non-hoarding families in our analysis, indicating that the extent of the continent effect is much broader than originally described. We investigated the potential role of minimal winter temperatures at the northernmost distribution borders in mediating continent effects. The effect of winter temperatures on HC volume was weak and it did not vary consistently along continents. We suggest that the general continental differences in relative HC size are independent of food hoarding and that its determinants should be sought among other ecological factors and life-history traits.

The Effect of Winter Temperature on Forest Tent Caterpillar (Lepidoptera: Lasiocampidae) Egg Survival and Population Dynamics in Northern Climates

Abstract Overwintering mortality of forest tent caterpillar [Malacosoma disstria (Hubner)] eggs was estimated over a 360 km2 grid of 83 plots in north-central Alberta over the period 1992–1996 during a local outbreak. Egg mortality in the trembling aspen (Populus tremuloides Michaux) canopy was generally low; however, 20% of the eggs laid in the summer of 1995 failed to hatch in the spring of 1996. In the shrub layer, 70% failed to hatch. In both the canopy and shrub layers, the spatial pattern of mortality was density-independent, with high mortality occurring in low-lying areas. Daily temperature records suggested that the proximal cause of death was freezing during mid-winter. Caterpillar populations peaked in 1995, before perturbation, and collapsed during the summer of 1996, largely as a result of larval parasitism. The timing of this perturbation-assisted population collapse coincided loosely with the penetration of larvae down into the shrub layer. We illustrate how winter temperature, albeit a den...

Cultivar Differences and the Effect of Winter Temperature on Flower Bud Development in Blackberry

Transition to reproductive development and subsequent development of floral primordia (e.g., sepals, petals, stamens, and pistils) were determined in several blackberry (Rubus subgenus Rubus Watson) cultivars (Boysen, Cherokee, Chester Thornless, Marion, and Thornless Evergreen) growing in one or more locations (Clarksville, Ark., Aurora and Hillsboro, Ore., and Kearneysville, W. Va.). Also, daily maximum, mean, and minimum temperatures were recorded at three sites (Clarksville, Aurora, and Kearneysville) for the September to April sampling period. In buds of `Boysen' and `Marion' from Oregon, sepal primordia were first observed in November and December, respectively. Further floral bud development continued into January. Sepal development in `Cherokee' buds occurred in October in Oregon and in December in Arkansas. At all three sites, the buds of `Chester Thornless' blackberry remained undifferentiated until spring. The average mean temperatures in Oregon were generally well above 5 °C during the bud sampling period, but were near 0 °C on most days from mid-December to January in Arkansas and from December to late-February in West Virginia. The phenology of flower bud differentiation varied among the cultivars and was strongly influenced by prevailing winter temperatures. The results suggest that the shortening day lengths of late summer trigger flower bud development in blackberry. Floral bud development in blackberry, once initiated, was continuous; however, periods of low temperature (<2 °C) can arrest development.

Effects of winter temperatures on gypsy moth egg masses in the Great Lakes region of the United States

Accurate prediction of winter survival of gypsy moth ( Lymantria dispar L.) eggs and phenology of egg hatch in spring are strongly dependent on temperature and are critical aspects of gypsy moth management programs. We monitored internal temperatures of egg masses at three heights aboveground level and at the four cardinal aspects on oak tree stems at two different locations in Michigan during the winter seasons of 1997/1998, 1998/1999 and 1999/2000. Effects of aspect were more strongly associated with observed egg mass temperatures than height above the ground surface. Instantaneous differences between egg mass temperatures on sunny days were as high as 30 °C greater on the southern aspect vs. egg mass temperatures on other aspects, resulting in substantial differences in pre-hatch growing degree accumulations for egg masses on a single tree. Egg masses on southern and western aspects, where solar loading and temperatures were greatest, experienced substantial mortality. Mean survival of eggs averaged across the three seasons was less than 25% on southern and western aspects, compared with averages of 53 and 73% on eastern and northern aspects, respectively. Linear regression of mean monthly egg mass–air temperature differences (between north and south aspects) and mean daily solar flux density resulted in slope coefficient estimates of 0.13 and 0.21 °C MJ m −2, and correlation coefficients of 0.81 and 0.82 at the two field locations, respectively. Using a simple egg mass hatch phenological model, such dissimilarities in temperature and growing degree day accumulation resulted in differences in estimated egg hatch dates of up to 25 days. Snow cover moderated egg mass temperature, with extreme seasonal minimum winter temperatures under snow cover as much as 7.1 °C warmer than those without snow cover.

The effect of winter temperatures on the timing of breeding activity in the common toad Bufo bufo.

A 19-year study of a common toad population in south Dorset, UK, was carried out between 1980 and 1998. The daily arrival of sexually mature male and female toads at a breeding pond was recorded each year. The timing of the main arrival of toads at the breeding pond was highly correlated with the mean daily temperatures over the 40 days immediately preceding the main arrival. When the temperatures were higher than average, breeding occurred significantly earlier in the year than if they were either average or lower than average. During the study, the toad breeding seasons were early (2-13 February) in 5 years (1989, 1990, 1993, 1995, 1998), late (16-23 March) in 2 years (1986, 1996) and average (25 February-8 March) during the remaining 12 years. Evidence was found suggesting that common toads have a daylength threshold of about 9 h, below which the migration to the breeding pond does not occur. Evidence was also found indicating that common toads in southern England have a threshold temperature for activity of about 6°C and that the onset of breeding activity is highly correlated with the number of days during the 40 days prior to the main arrival at the breeding pond that were at or above this temperature. Predicting the start of the main breeding migration to a pond in any year may be possible by comparing the pattern of the 40-day running mean daily temperatures from 21 December the preceding year with those from previous years when the start of breeding activity is known. Although all five of the earliest recorded toad breeding years occurred during the last 10 years, and were associated with the occurrence of particularly mild winters, a significant trend towards earlier breeding in recent years compared with previous years was not found.

Effect of Winter Temperature on Wild Turkey Metabolism

We used indirect calorimetry to measure the effects of air temperature (T a ), age class, and body mass on metabolic rates of 9 adult and 7 juvenile female eastern wild turkeys (Meleagris gallopavo silvestris) during winter. Previous studies produced disparate results on this important aspect of winter ecology of wild turkeys. Standard metabolic rates (SMRs) of adult and juvenile hens were not different (P = 0.122) and averaged 28.69 mL O 2 .min -1 .bird -1 . Wild turkey metabolism increased with decreasing T a (P < 0.001) below the lower critical temperature (T lc ) of 10.9°C. Metabolic rates were not related to body mass (P = 0.571), and age-specific metabolic rates were not distinguishable (P = 0.998). We estimated that a flock of 20 hens would need to find 400 g/day of additional food to meet thermoregulatory demands for each 10°C drop in T a below 10.9°C.

Effects of winter temperature and feeding regime on the rate of early maturation in Atlantic salmon ( Salmo salar) male parr

Individually identified Atlantic salmon parr were submitted to different combinations of temperature and feeding regime during their first winter. These treatments were designed to test for causal relationships between winter growth, body lipid level in spring as measured by the condition factor, and subsequent maturation. Maturation was observed almost exclusively in the lower modal group (presumptive 2-year-old smolts). Large and significant differences in winter growth performance and condition factor in spring were observed among treatments. Some variation in the rate of male parr maturation was observed among treatments as well, but the differences were not significant. The pattern of growth and change in condition factor before male parr maturation were different from that which had been observed before grilse and post-smolt maturation. The results of this study suggest that the threshold for lipid storage which initiates male parr maturation might be very low, and male parr maturation is thus not very dependent upon winter growth and spring lipid storage level.

Effects of Winter Temperature and Predation on the Abundance of Alewife ( Alosa pseudoharengus) in the Bay of Quinte, Lake Ontario

Alewife ( Alosa pseudoharengus) abundance in the Bay of Quinte, Lake Ontario, was monitored with a bottom trawl survey from 1972 to 1987. Prior to 1977, alewife catch-per-effort (CPE) was high in all areas of the bay but declined drastically following unusually cold winters in 1976–77 and 1977–78. Beginning in 1980, alewife CPE recovered in the lower bay, adjacent to Lake Ontario. This recovery was not observed in the upper bay where predation by a resurgent walleye ( Stizostedion vitreum) population maintained the reduced numbers of alewife. We conclude that walleye predation has played an important role in generating differences in alewife abundance between the upper and lower bays since 1980. There is a negative correlation between adult alewife CPE and young-of-year (YOY) alewife CPE suggesting that intraspecific predation is an important factor in the production of YOY alewife in the Bay of Quinte. Recruitment mechanisms for alewife in the Bay of Quinte may depend more on intraspecific predation, in contrast to Lake Ontario where intraspecific competition for zooplankton has been hypothesized as a limiting factor.

Factors Affecting the Distribution of Mallards Wintering in the Mississippi Alluvial Valley

Abstract The Mississippi Alluvial Valley (MAV) is the principal wintering area for Mallards (Anas platyrhynchos) in the Mississippi Flyway. Here, we consider it a distinct habitat (sensu Fretwell 1972), i.e. fitness is relatively homogeneous among ducks within the MAV but different from that of ducks in other such habitats. We analyzed recovery distributions of Mallards banded preseason (July-September 1950-1980) to test hypotheses concerning the effects of winter temperatures, precipitation, and population levels on Mallard winter distribution. When two groups of years that comprised extremes of warm and cold winter weather were compared, recovery distributions of all four age and sex classes (adult males and females, young males and females) differed significantly; recoveries were located farther south in cold years. Recovery distributions also differed between wet and dry years in the MAV for all groups except adult males, higher proportions of recoveries of adult females and of young males and females occurring in the MAV during wet winters. Although differences in continental Mallard population size were associated with differences in recovery distributions only of adult males and young females, the proportion of young males and of all young Mallards recovered in the MAV increased during years of low populations. We conclude that temperature, water conditions, and population size affect the habitat suitability of Mallard wintering areas and that Mallards exhibit considerable flexibility in winter distribution associated with these factors.

Winter Mortality of Larvae of the European Pine Shoot Moth, Rhyacionia Buoliana Schiff., in Connecticut

The severity of the winter of 1933–34 in contrast with the two previous winters afforded the writer the opportunity of observing the effect of winter temperatures on the survival of larvae of the European pine shoot moth. These observations are included here together with the results of some laboratory experiments on lethal low temperatures. An explanation is suggested for the course of development of the shoot moth outbreak since the introduction of the insect into Connecticut in 1914.