Overwintering Season Research Articles

Trends Observed in Fall Migrant Monarch Butterflies (Lepidoptera: Nymphalidae) East of the Appalachian Mountains at an Inland Stopover in Southern Pennsylvania over an Eighteen Year Period

In total, 11,333 fall migrant monarch butterflies were captured, measured, tagged, and released in southern Pennsylvania over an 18-yr period from 1992 to 2009, excluding 1996 and 2004. Fifty-six (0.494%) were recovered at the Mexican overwintering sites. Hind wing tags had a much higher recovery rate (1.13%) than forewing tags (0.138%). When compared with published recovery rates east of the Appalachians using the same tag type, Pennsylvania was higher than all coastal sites but similar to that of inland Virginia, indicating that inland migrants are more successful. Six U.S. recoveries indicate that monarchs experience considerable eastward wind displacement after leaving the tagging sites. The wild monarchs were divided into three groups for analysis: early (20 Aug–9 Sep), middle (10 Sep–1 Oct), and late (2 Oct–20 Oct) to determine temporal trends. The average forewing length decreased over time, while the percentage of female migrants increased. These trends were not seen in a comparison set of raised monarchs originating from the same general area. As over half the Mexican recoveries came from storm-killed fall 2003 migrants, recoveries were analyzed with and without 2003, and for 2003 alone. More early than middle migrants and no late migrants were recovered. Female migrants were more likely to be recovered from 2003 and overall, but not when 2003 was excluded. The recovery data suggest that males are less likely to make it to Mexico and suffer higher mortality once there during normal overwintering seasons. It also suggests that while early migration is beneficial to both genders, it is even more beneficial for females.

An Evaluation of Butterfly Gardens for Restoring Habitat for the Monarch Butterfly (Lepidoptera: Danaidae).

The eastern migratory monarch butterfly (Danaus plexippus L.) population in North America hit record low numbers during the 2013-2014 overwintering season, prompting pleas by scientists and conservation groups to plant the butterfly's milkweed host plants (Asclepias spp.) in residential areas. While planting butterfly gardens with host plants seems like an intuitive action, no previous study has directly compared larval survival in gardens and natural areas to demonstrate that gardens are suitable habitats for Lepidoptera. In this study, milkweed was planted in residential gardens and natural areas. In 2009 and 2010, plants were monitored for oviposition by monarch butterflies and survival of monarch eggs and caterpillars. Monarchs oviposited significantly more frequently in gardens than in natural sites, with 2.0 and 6.2 times more eggs per plant per observation in 2009 and 2010, respectively. There were no significant differences in overall subadult survival between gardens and natural areas. Significant differences in survival were measured for egg and larval cohorts when analyzed separately, but these were not consistent between years. These results suggest that planting gardens with suitable larval host plants can be an effective tool for restoring habitat for monarch butterflies. If planted over a large area, garden plantings may be useful as a partial mitigation for dramatic loss of monarch habitat in agricultural settings.

Finding the best predictor of reproductive performance of Leach's Storm-Petrels

ABSTRACT Physiological and environmental factors shape foraging strategies and energy balance. For species that breed seasonally, physiological changes in an individual can have short-term effects, but also can persist as carry-over effects from one season to the next, such as from the overwintering season to the breeding season. We tested the hypothesis that reproductive performance could be predicted by diet and energy balance during the breeding and nonbreeding seasons in a long-lived seabird, the Leach's Storm-Petrel (Oceanodroma leucorhoa). Specifically, we predicted that better reproductive performance would be correlated with four factors: (1) a high-lipid diet, as indexed by a high C:N ratio in stable isotope analyses; (2) a diet rich in antioxidants, as indexed by high plasma antioxidant capacity; (3) foraging at a high trophic level, as indexed by high values of δ15N in stable isotope analyses, which is positively related to lipids; and (4) a positive long-term energy balance, revealed by low le...

Estimation of nutrient input by a migratory bird, the Tundra Swan (Cygnus columbianus), to winter-flooded paddy fields

Thousands of Tundra Swans visit winter-flooded paddy fields in the study area, Yasugi city, Shimane Prefecture, Japan every year for overwintering from November to March. Since 2004, they have roosted in the paddy fields during the night and foraged in the paddy and surrounding fields during the day, coinciding with the time when farmers began using winter-flooded paddy fields. Before 2004, the swans visited the area for foraging during the day and roosted at nearby lakes, wetlands, and sandbars along rivers during the night. When the swans visited our target paddy fields, the water gradually became green and began to emit an ammonia-like odor. In this study, we investigated the changes in the water qualities of winter-flooded paddy fields and the influence of bird excrement on water quality in the paddy fields during winter, and then estimated the amounts of nitrogen (N) and phosphorus (P) provided by bird droppings to the paddy fields. The mean concentrations of N, P, suspended sediment, and total organic carbon were higher in the overwintering season than during the irrigation season. This trend was observed in both the first and second seasons of the study. The spatial distribution of electric conductivity (EC) measured using a GEM-2 broad-band electromagnetic sensor coincided with that of the matted sites of Tundra Swans in the paddy field, which indicated that the excrement of the swans affected the EC distribution. The total input amounts of N and P from the birds’ excrement to the flooded paddy fields were estimated using a simple model that considered bird counts and probable nutrient content of feces, and the amounts were found to be equivalent to approximately 30% of those present in the standard fertilizers used for rice during the irrigation period. These results suggested that the excrement from the swans markedly influences the water qualities of winter-flooded paddy fields.

Impact of Climate Change on the Distribution ofAedes albopictus(Diptera: Culicidae) in Northern Japan: Retrospective Analyses

The impact of climate change on the distribution of Aedes albopictus (Skuse) was analyzed in northern Japan, where chronological distribution records are incomplete. We analyzed local climate data using linear regression of the thermal suitability index (TSI) for the mosquito and mean annual temperature as functions of time. In northern Japan, thermal conditions since the early 20th century have become increasingly suitable for Ae. albopictus, more as a result of decreasing coldness in the overwintering season than increasing warmth in the reproductive season. Based on recent discovery records of Ae. albopictus in the northern border range, we determined thermal criteria for estimating when its persistent establishment became thermally possible. Retrospective analyses indicated that those criteria were reached in most coastal lowlands of northern Honshu before the accelerated temperature increase after the mid-1980s and the first records of this species after 1990; at some sites, temperature criteria were reached during or before the early 20th century. Expansion of the thermally suitable range after 1990 was supported only for inland areas and the northernmost Pacific coast. The estimated expansion rate was approximately 26 km per decade. Our analyses also demonstrated the importance of local climate heterogeneity (apart from north-south or altitudinal temperature gradients) in determining the expansion pattern.

Impact of climate change scenarios on Canadian agroclimatic indices

Qian, B., De Jong, R., Gameda, S., Huffman, T., Neilsen, D., Desjardins, R., Wang, H. and McConkey, B. 2013. Impact of climate change scenarios on Canadian agroclimatic indices. Can. J. Soil Sci. 93: 243–259. The Canadian agricultural sector is facing the impacts of climate change. Future scenarios of agroclimatic change provide information for assessing climate change impacts and developing adaptation strategies. The goal of this study was to derive and compare agroclimatic indices based on current and projected future climate scenarios and to discuss the potential implications of climate change impacts on agricultural production and adaptation strategies in Canada. Downscaled daily climate scenarios, including maximum and minimum temperatures and precipitation for a future time period, 2040–2069, were generated using the stochastic weather generator AAFC-WG for Canadian agricultural regions on a 0.5°×0.5° grid. Multiple climate scenarios were developed, based on the results of climate change simulations conducted using two global climate models – CGCM3 and HadGEM1 – forced by IPCC SRES greenhouse gas (GHG) emission scenarios A2, A1B and B1, as well as two regional climate models forced by the A2 emission scenario. The agroclimatic indices that estimate growing season start, end and length, as well as heat accumulations and moisture conditions during the growing season for three types of field crops, cool season, warm season and over-wintering crops, were used to represent agroclimatic conditions. Compared with the baseline period 1961–1990, growing seasons were projected to start earlier, on average 13 d earlier for cool season and over-wintering crops and 11 d earlier for warm season crops. The end of the growing season was projected on average to be 10 and 13 d later for over-wintering and warm season crops, respectively, but 11 d earlier for cool season crops because of the projected high summer temperatures. Two indices quantifying the heat accumulation during the growing season, effective growing degree days (EGDD) and crop heat units (CHU) indicated a notable increase in heat accumulation: on average, EGDD increased by 15, 55 and 34% for cool season, warm season and over-wintering crops, respectively. The magnitudes of the projected changes were highly dependent on the climate models, as well as on the GHG emission scenarios. Some contradictory projections were observed for moisture conditions based on precipitation deficit accumulated over the growing season. This confirmed that the uncertainties in climate projections were large, especially those related to precipitation, and such uncertainties should be taken into account in decision making when adaptation strategies are developed. Nevertheless, the projected changes in indices related to temperature were fairly consistent.

Adaptive Significance of Previously Mated Monarch Butterfly Females (Danaus plexippus(Linneaus)) Overwintering at a California Winter Site

In the fall, migrating monarch butterflies are in reproductive diapause when they arrive at winter sites in California. Approximately 1/3 of the overwintering females contain sperm of summer males within their spermatheca. When these females were subjected to conditions that terminated diapause, they were able to produce offspring with near equal fecundity throughout the overwintering period. The mated females also benefited by the added male nutrients to produce eggs when their body energy reserves were low. Spring matings of virgin females are necessary to obtain spermatozoa to fertilize their eggs and possibly to receive male nutrients to supplement their energy reserves. Several possible survival advantages of early mating are: (1) previously mated females are better able to withstand the rapid ovarian development towards the end of the overwintering season than virgin females; (2) females need not mate again to insure the fecundity of her eggs; and (3) mating with previous summer males broadens the genetic plasticity of the species.

Environmental and demographic determinants of avian influenza viruses in waterfowl across the contiguous United States.

Outbreaks of avian influenza in North American poultry have been linked to wild waterfowl. A first step towards understanding where and when avian influenza viruses might emerge from North American waterfowl is to identify environmental and demographic determinants of infection in their populations. Laboratory studies indicate water temperature as one determinant of environmental viral persistence and we explored this hypothesis at the landscape scale. We also hypothesized that the interval apparent prevalence in ducks within a local watershed during the overwintering season would influence infection probabilities during the following breeding season within the same local watershed. Using avian influenza virus surveillance data collected from 19,965 wild waterfowl across the contiguous United States between October 2006 and September 2009 We fit Logistic regression models relating the infection status of individual birds sampled on their breeding grounds to demographic characteristics, temperature, and interval apparent prevalence during the preceding overwintering season at the local watershed scale. We found strong support for sex, age, and species differences in the probability an individual duck tested positive for avian influenza virus. In addition, we found that for every seven days the local minimum temperature fell below zero, the chance an individual would test positive for avian influenza virus increased by 5.9 percent. We also found a twelve percent increase in the chance an individual would test positive during the breeding season for every ten percent increase in the interval apparent prevalence during the prior overwintering season. These results suggest that viral deposition in water and sub-freezing temperatures during the overwintering season may act as determinants of individual level infection risk during the subsequent breeding season. Our findings have implications for future surveillance activities in waterfowl and domestic poultry populations. Further study is needed to identify how these drivers might interact with other host-specific infection determinants, such as species phylogeny, immunological status, and behavioral characteristics.

Effects of hunting season structure, weather and body condition on overwintering mallard Anas platyrhynchos survival

AbstractInformation on waterfowl survival during the overwintering season (i.e. autumn and winter), when hunting seasons occur, is important for making harvest management decisions. However, the relationship of overwintering survival to hunting season structure, weather and body condition are not well understood. We measured survival of 235 radio‐marked adult female and male mallards Anas platyrhynchos along the South Platte River corridor in northeastern Colorado, USA, during the overwintering seasons of 2005/06 (pilot year), 2006/07 and 2007/08, and we determined the primary factors affecting survival. Hunting was the most important factor affecting survival. Of mortality, 67% were direct results of hunting, and survival was lower during hunting periods compared to non‐hunting periods. Within hunting periods, survival was lowest during the first 2‐3 weekends of the hunting periods. During the seasons 2006/07 and 2007/08, survival of radio‐marked mallards was monitored during September‐February. The estimated survival was 0.65 (95% CI = 0.50 ‐ 0.78) for females and 0.54 (95% CI = 0.39 ‐ 0.68) for males during 2006/07, and 0.55 (95% CI = 0.40 ‐ 0.69) for females and 0.42 (95% CI = 0.28 ‐ 0.58) for males during 2007/08. We did not observe a strong correlation between body condition index and survival ( = 0.36, SE = 0.43). Accumulated snowfall and daily minimum temperature were unimportant variables for predicting survival. Of hunting recoveries, 89% occurred in our study area, and 15% and 18% of radio‐marked mallards went missing during 2006/07 and 2007/08, respectively. Our results suggest that split hunting seasons are an effective management tool to increase hunter harvest and affect overwintering survival. Given a set bag limit and season length, managers may be able to increase hunter harvest by: 1) having hunting periods of at least three weeks in length, 2) including as many weekend days (i.e. Saturdays and Sundays) within hunting periods as possible and 3) interspersing hunting periods with non‐hunting periods of at least 2‐3 weeks.

Genetic Analysis on Overwintering Character of Glutinous Rice 89–1

Abstract This article discusses the overwintering ability and genetic variation of the main agronomic traits in a new germplasm resource, glutinous rice 89–1. Survival rates of overwintering axillary buds and stems were observed in different altitudes. The F 1, backcross F 1 and F 2 populations were constructed from sexual crossing between glutinous rice 89–1 and Hongmangnuo, Fuhui 838, Minghui 63, Ce 64. The overwintering ability and genetic variation of the main agronomic traits were analyzed in different seasons. Results showed that glutinous rice 89–1 could overwinter by axillary buds in low temperatures at different altitudes. Axillary buds would ratoon in the following year. The survival rates of rice stem and axillary buds were 82.6 and 29%, respectively. The grain yields were 6291.0 kg ha −1 in the overwintering ratooning season, and corresponded in the main season. Genetic analysis and chi-square test showed that the overwintering ability of glutinous rice 89–1 was likely controlled by polygene, and heritabilities showed diversity in different hybrid combinations. The highest heritabilities of 1000-grain weight and plant height were in the main crop season, whereas the lowest were in the overwintering season, and the heritabilities of grain numbers per panicle and the seed setting rate reached the highest in the ratooning season. The spikelets per panicle, the seed setting rate, the 1000-grain weight, the plant height, and the spikelet length had nearly normal distribution in F 2 populations of glutinous rice 89–1/Minghui 63, but the seed setting rate had bimodal distribution. Overwintering glutinous rice 89–1 was a useful new genetic germplasm resource.

Use of Posthatching Yolk and External Forage to Maximize Early Growth in Apalone Mutica Hatchlings

Posthatching yolk in oviparous vertebrates is thought to supply the hatchling with energy for a period of time after hatching in habitats that might require fasting. To examine strategies of posthatching energy use in Apalone mutica, hatchlings were fed or not fed over periods of nine weeks in 2003 and six weeks in 2004. Mass, plastron length, carapace width, and body condition changed during the course of the experiment; all trajectories of change, except carapace width in 2004, differed between fed and unfed hatchlings. Trajectories of fed hatchlings were significantly higher than unfed hatchlings. Fed and unfed hatchlings used internalized yolk at similar rates: 50% of the yolk was depleted by day eight after hatching and 90% by day 27. Metabolic rate (approximately 0.236 ml CO2 h−1) did not differ between fed and unfed hatchlings. Yolk reserves are insufficient to sustain hatchlings to the first overwintering season, but with access to external forage, hatchlings appear to use yolk reserves to meet maintenance demands to support maximal growth.

瀬戸内海東部海域におけるマダイの食性とその季節変化

The feeding habit of red sea bream, Pagrus major, was examined by stomach content analysis with special reference to its seasonal changes in Tomogashima Channel waters, an important habitat in the eastern Seto Inland Sea. The fish fed through its life on many kinds of organisms, but intensively on a few kinds of them during the feeding season from spring to autumn. It was noted here that juveniles fed on zooplankton such as Acartia omorii and Oikopleura sp. from June to July, and youngs on the pasiphaeid shrimps Leptochela from August onward. These shrimps were in fact the main prey for the fish of age 1 and over. The stomach contents were poor and changed after November, because of the fall in water temperature and the increase in its population density with overwintering assemblage. Consequently, until March, or the end of the overwintering season, fish growth was retarded with a continuous decrease in the condition factor. The change in feeding habit with the winter assemblage was most remarkable for age 0 fish. The winter season would appear to be a critical period for the survival of the fish especially at this age.

Behavioral and ecological interactions of foraging mice (Peromyscus melanotis) with overwintering monarch butterflies (Danaus plexippus) in México.

Mice (Peromyscus melanotis) immigrate extensively to overwintering colonies of monarch butterflies (Danaus plexippus) in México. There they feed on both live and dead butterflies that accumulate on the ground and in low vegetation. Through a series of feeding experiments, we examined the potential impact of mouse predation on these colonies, as well as how this predation was influenced by the accessibility and the degree of desiccation of the monarchs. Mice attacked on average 39.9 wet (freshlykilled) butterflies per night. We estimated that a population of mice (75-105 individuals) could kill approximately 0.40-0.57 million butterflies in a 1 ha colony (4-5.7% of the colony) over the 135-day overwintering season. In feeding experiments, mice fed disproportionately on: 1) wet (hydrated) monarchs close to the ground versus those perched higher; 2) wet monarchs, when both wet and dry (desiccated) monarchs were on the ground; and 3) wet monarchs on stakes versus dry monarchs on the ground. Mice commonly ate the entire abdomen of dry monarchs, whereas they fed selectively on the abdomen of wet monarchs by discarding the bitter, cardenolide-laden cuticle and eating the internal tissues. These results suggest that the monarchs' state of desiccation is more important than their accessibility in determining the feeding preferences of these mice. However, the monarchs' strong tendency to crawl up vegetation does appear to reduce their risk to mouse predation.

Seasonal Levels of Abscisic Acid in Buds and Stems of Acer saccharum

AbstractChanges in abscisic acid (ABA) were followed in the buds and youngest stems of 6‐year‐old sugar maple (Acer saccharum Marsh.) saplings at approximately monthly intervals during the year. High levels present in the buds in July and August showed a moderate decline through early October, but subsequently increased following leaf fall and reached the maximum values detected during the study in November and December. Thereafter ABA fell sharply, reaching its lowest point immediately prior to budbreak in early May. While ABA in the stems followed a somewhat similar pattern, only minor changes were observed in the relatively low values detected between June and November. Except for the spring months, when concentrations of ABA in the stems and buds were at minimum levels, the buds always contained several times more inhibitor per unit dry weight of tissue. Analysis of selected samples from both tissues showed that bound (alkaline‐hydrolyzable) ABA increased during the overwintering season, with the highest values noted in the spring. Although the patterns of change observed in this study are indicative of a role for ABA in the overwintering process, ABA does not appear to be the primary endogenous factor responsible for initiation of the dormant state.