Variable effects of climate change on six species of North American birds

Many recent studies have shown that birds are advancing their laying date in response to long-term increases in spring temperatures. These studies have been conducted primarily in Europe and at local scales. If climate change is a large-scale phenomenon, then we should see responses at larger scales and in other regions. We examined the effects of long-term temperature change on the laying dates and clutch sizes of six ecologically diverse species of North American birds using 50 years of nest record data. As predicted, laying dates for most (four of six) species were earlier when spring temperatures were warmer. Over the long-term, laying dates advanced over time for two species (red-winged blackbirds, Agelaius phoeniceus and eastern bluebirds, Sialia sialis). Laying date of song sparrows (Melospiza melodia) also advanced with increasing temperature when the analysis was restricted to eastern populations. Neither laying date nor clutch sizes changed significantly over time in the remaining species (American coot, Fulica americana, killdeer, Charadrius vociferous, and American robin, Turdus migratorius), an unsurprising result given the lack of increase in temperatures over time at nest locations of these species. This study indicates that the relationship between climate change and breeding in birds is variable within and among species. In large-scale analyses of North American birds, four of seven species have shown advances in laying dates with increasing temperature (including song sparrows in the east). These variable responses within and among species highlight the need for more detailed studies across large spatial scales.     

Variation in laying date in relation to spring temperature in three species of tits (Paridae) and pied flycatchers Ficedula hypoleuca in southernmost Sweden

This study documents the advancement of laying dates in three species of tits (Paridae) in southernmost Sweden during recent decades, and the absence of a similar response in the pied flycatcher Ficedula hypoleuca. It is based on several different nestbox studies; the oldest one starting in 1969. During 1969 to 2012, mean spring temperatures in the study area increased by between 0.06 and 0.08°C per year, depending on the period considered. Great tits Parus major, blue tits Cyanistes caeruleus and marsh tits Poecile palustris, which generally start egg laying between the last week of April and the first week of May, all advanced laying date at a similar rate during the study period (0.25 d yr^–1). This indicates that these species were similarly affected by increasing temperatures. When accounting for mean spring temperature variation, we still found an advancement of laying date over the study period, mostly due to such relationships among marsh and blue tits. This result could reflect ongoing microevolution favouring earlier laying, but could also be a result of other factors such as increased intra‐ or inter‐specific competition for early breeding. Pied flycatchers, which generally lay during the third week of May, did not significantly advance the date of egg laying despite that the long‐term trend in the increase in ambient temperature during the 30‐d period preceding the start of egg laying was similar for pied flycatchers compared to the tit species.     

Latitudinal variation in blue tit and great tit nest characteristics indicates environmental adjustment

Aim The laying of eggs and the building of a nest structure to accommodate them are two of the defining characteristics of members of the class Aves. Nest structures vary considerably across avian taxa and for many species the structure of the completed nest can have important consequences both for parents and their offspring. While nest characteristics are expected to vary adaptively in response to environmental conditions, large‐scale spatial variation in nest characteristics has been largely overlooked. Here, we examine the effects of latitudinal variation in spring temperatures on nest characteristics, including insulatory properties, and reproductive success of blue tits, Cyanistes caeruleus, and great tits, Parus major. Location Great Britain. Methods Nests and reproductive data were collected from seven study sites, spread over 5° of latitude. The nest insulatory properties were then determined before the nests were separated into nest base material and cup lining material. Results As spring temperatures increased with decreasing latitude, the mass of the nest base material did not vary in either species, while the mass of the cup lining material and nest insulatory properties decreased in both species. This suggests that in response to increasing temperatures the breeding female reduces the mass of the cup lining material, thereby maintaining an appropriate microclimate for incubating and brooding. The mean first egg date of both species advanced with decreasing latitude and increasing spring temperatures, although clutch size and brood size at hatching and fledging did not vary. Main conclusions This is the first study to demonstrate that the nest‐construction behaviour of birds varies in response to large‐scale spatial variation in ambient temperatures. Therefore, nest composition reliably indicates environmental conditions and we suggest that studies of nest structure may be sentinels for the early signs of rapid climate change.     

Multiple responses to increasing spring temperatures in the breeding cycle of blue and great tits (Cyanistes caeruleus,Parus major)

Many bird species start laying their eggs earlier in response to increasing spring temperatures, but the causes of variation between and within species have not been fully explained. Moreover, synchronization of the nestling period with the food supply not only depends on first‐egg dates but also on additional reproductive parameters including laying interruptions, incubation time and nestling growth rate. We studied the breeding cycle of two sympatric and closely related species, the blue tit Cyanistes caeruleus and the great tit Parus major in a rich oak‐beech forest, and found that both advanced their mean first‐egg dates by 11–12 days over the last three decades. In addition, the time from first egg to fledging has shortened by 2–3 days, through a decrease in laying interruptions, incubation time (not statistically significant) and nestling development time. This decrease is correlated with a gradual increase of temperatures during laying, suggesting a major effect of the reduction in laying interruptions. In both species, the occurrence of second clutches has strongly decreased over time. As a consequence, the average time of fledging (all broods combined) has advanced by 15.4 and 18.6 days for blue and great tits, respectively, and variance in fledging dates has decreased by 70–75%. Indirect estimates of the food peak suggest that both species have maintained synchronization with the food supply. We found consistent selection for large clutch size, early laying and short nest time (laying to fledging), but no consistent changes in selection over time. Analyses of within‐individual variation show that most of the change can be explained by individual plasticity in laying date, fledging date and nest time. This study highlights the importance of studying all components of the reproductive cycle, including second clutches, in order to assess how natural populations respond to climate change.     

Effects of climate variation on timing of nesting,reproductive success,and offspring sex ratios of red-winged blackbirds

Predicting ecological consequences of climate change will be improved by understanding how species are affected by contemporary climate variation, particularly if analyses involve more than single ecological variables and focus on large-scale climate phenomena. I used 18 years of data from red-winged blackbirds (Agelaius phoeniceus) studied over a 25-year period in eastern Ontario to explore chronological and climate-related patterns of reproduction. Although blackbirds started nesting earlier in years with warmer springs, associated with low winter values of the North Atlantic Oscillation Index (NAOI), there was no advance in laying dates over the study. Nesting ended progressively later and the breeding season lasted longer over the study, however, associated with higher spring values of NAOI. As the length of the nesting season increased, offspring sex ratios became more female biased, apparently as a result of females adjusting the sex of the eggs they laid, rather than from sex-biased nestling mortality. Clutch size did not vary systematically over the study or with climate. Opposing trends of declining nest success and increasing productivity of successful nests over the study resulted in no chronological change in productivity per female. Higher productivity of successful nests was associated with higher winter NAOI values, possibly because synchrony between nesting and food availability was higher in years with high NAOI values. Other than the association between the start of nesting and spring temperatures, local weather (e.g., temperature, rainfall) patterns that linked NAOI with reproduction were not identified, suggesting that weather patterns may be complex. Because climate affected most aspects of red-winged blackbird reproduction examined, focusing on associations between climate and single variables (e.g., first-egg dates) will have limited value in predicting how future climates will affect populations.     

Climatic effects on arrival and laying dates in a long-distance migrant, the Collared Flycatcher Ficedula albicollis

Long‐distance migrants may respond to climate change in breeding, wintering or staging area by changing their phenology. The geographical variation in such responses (e.g. coastal vs. continental Europe) and the relative importance of climate at different spatial scales remain unclear. Here we analysed variation in first arrival dates (FADs) and laying dates of the Collared Flycatcher Ficedula albicollis in a central European population, from 1973 to 2002. The North Atlantic Oscillation (NAO) index correlated weakly with local temperature during the laying period. Decreasing spring temperatures until 1980 were associated with a trend towards later laying. The rate of warming (0.2 °C per year) and laying advancement (0.4 days per year) since 1980 are amongst the highest values reported elsewhere. This long‐term trend in laying date was largely explained by the change in climatic factors. The negative effect of local spring temperature on laying was relatively stronger than that of NAO. The number of clutches initiated on a particular day was marginally affected by the temperature 3 days prior to laying and the response of females to daily variation in temperature did not change over years. Correspondence between the average population‐level and the individual‐level responses of laying date to climate variation suggests that the advancement of laying was due to phenotypic plasticity. Despite warmer springs and advanced laying, FADs did not change over years and were not correlated with local spring temperature. Marginal evidence suggests later departure from wintering grounds and faster migration across staging areas in warmer conditions. Advancement of arrival was probably constrained by low local temperatures in early spring just before arrival that have not changed over years. The interval between first arrival and laying has declined since 1980 (0.5 days per year), but the increasing temperature during that period may have kept the food supply approximately unchanged.     

Reproductive ecology of the jacky dragon (Amphibolurus muricatus): an agamid lizard with temperature‐dependent sex determination

Abstract The jacky dragon, Amphibolurus muricatus (White, ex Shaw 1790) is a medium sized agamid lizard from the southeast of Australia. Laboratory incubation trials show that this species possesses temperature‐dependent sex determination. Both high and low incubation temperatures produced all female offspring, while varying proportions of males hatched at intermediate temperatures. Females may lay several clutches containing from three to nine eggs during the spring and summer. We report the first field nest temperature recordings for a squamate reptile with temperature‐dependent sex determination. Hatchling sex is determined by nest temperatures that are due to the combination of daily and seasonal weather conditions, together with maternal nest site selection. Over the prolonged egg‐laying season, mean nest temperatures steadily increase. This suggests that hatchling sex is best predicted by the date of egg laying, and that sex ratios from field nests will vary over the course of the breeding season. Lizards hatching from eggs laid in the spring (October) experience a longer growing season and should reach a larger body size by the beginning of their first reproductive season, compared to lizards from eggs laid in late summer (February). Adult male A. muricatus attain a greater maximum body size and have relatively larger heads than females, possibly as a consequence of sexual selection due to male‐male competition for territories and mates. If reproductive success in males increases with larger body size, then early hatching males may obtain a greater fitness benefit as adults, compared to males that hatch in late summer. We hypothesize that early season nests should produce male‐biased sex ratios, and that this provides an adaptive explanation for temperature‐dependent sex determination in A. muricatus.     

Temperature during egg formation and the effect of climate warming on egg size in a small songbird

The predicted effects of recent climate warming on egg size in birds are controversial, as only two long-term studies have been reported, with contrasting results. Long-term data on egg size variation are analyzed in relation to ambient temperatures in a southern European population of pied flycatchers where breeding phenology has not matched the spring advancement in the last decades. Cross-sectional, population analyses indicated that egg breadth, but not egg length, has decreased significantly along the 16-year period, leading to marginally non-significant decreases in egg volume. Longitudinal, individual analyses revealed that despite females consistently laying larger eggs when they experienced warmer temperatures during the prelaying and laying periods, there was an overall negative response – i.e. decreasing egg volume and breadth with increasing spring (May) average temperatures – across individuals. This trend is hypothesised to be caused by the mismatched breeding phenology, in relation to climate warming, of this population. Except in the unlikely cases of populations capable of perfectly synchronising their phenology to changes in their environment, maladjustments are likely for traits such as egg size, which depend strongly on female condition. Slight changes or absence thereof in breeding dates may be followed by mismatched dates, in terms of food abundance, for optimal egg formation, which would be reflected in smaller average egg size, contrary to early predictions on the effects of climate warming on bird egg size.     

Studies on the oviposition and longevity ofIlione albiseta [Dipt.: Sciomyzidae] — Potential biological control agent of liver fluke

The effect of 5 constant temperatures (10, 14, 17, 20 and 23°C) on the oviposition and longevity ofIlione albiseta was investigated. Most eggs were laid at 14–17°C and mean oviposition period declined progressively above and below 14°C. There was no significant difference between oviposition rates or preoviposition periods at each constant temperature, but the mean number of days between egg laying for each female was significantly greater at 10 °C than at 17, 20 and 23 °C than at 20 °C. The percentage of infertile eggs laid ranged from 9.2% at 23 °C to 17.9 % at 20 °C and these eggs tended to be laid at the beginning and end of each oviposition period. A possible association between sex ratio of the emergent adult and temperature is also discussed.      

Crop planting dates: an analysis of global patterns

Aim To assemble a data set of global crop planting and harvesting dates for 19 major crops, explore spatial relationships between planting date and climate for two of them, and compare our analysis with a review of the literature on factors that drive decisions on planting dates. Location Global. Methods We digitized and georeferenced existing data on crop planting and harvesting dates from six sources. We then examined relationships between planting dates and temperature, precipitation and potential evapotranspiration using 30‐year average climatologies from the Climatic Research Unit, University of East Anglia (CRU CL 2.0). Results We present global planting date patterns for maize, spring wheat and winter wheat (our full, publicly available data set contains planting and harvesting dates for 19 major crops). Maize planting in the northern mid‐latitudes generally occurs in April and May. Daily average air temperatures are usually c. 12–17 °C at the time of maize planting in these regions, although soil moisture often determines planting date more directly than does temperature. Maize planting dates vary more widely in tropical regions. Spring wheat is usually planted at cooler temperatures than maize, between c. 8 and 14 °C in temperate regions. Winter wheat is generally planted in September and October in the northern mid‐latitudes. Main conclusions In temperate regions, spatial patterns of maize and spring wheat planting dates can be predicted reasonably well by assuming a fixed temperature at planting. However, planting dates in lower latitudes and planting dates of winter wheat are more difficult to predict from climate alone. In part this is because planting dates may be chosen to ensure a favourable climate during a critical growth stage, such as flowering, rather than to ensure an optimal climate early in the crop's growth. The lack of predictability is also due to the pervasive influence of technological and socio‐economic factors on planting dates.     

Interannual variations of reproductive parameters in a booted eagle (Hieraaetus pennatus) population: the influence of density and laying date

A population of booted eagles (Hieraaetus pennatus) consisting of 21–29 pairs was studied for 7 years (1998–2004) in a forested mountainous region of southeastern Spain. The average egg-laying time was 25 April (earliest 31 March, latest 26 May). Sixty-eight percent of territorial pairs produced eggs, and 81% of reproductive pairs successfully raised at least one offspring. Mean clutch size was 1.91 eggs, and 84% hatched. The survival rate of chicks was high, with only 17% dying. The major known cause of nestling mortality was predation, mainly by the Eurasian eagle owl (Bubo bubo). The mean number of flying offspring was 0.91 per territorial pair, 1.29 per reproductive pair and 1.65 per successful pair. All population breeding parameters analysed were density independent, but most showed a significantly negative relationship with mean laying date.     

Best environmental predictors of breeding phenology differ with elevation in a common woodland bird species

Temperatures in mountain areas are increasing at a higher rate than the Northern Hemisphere land average, but how fauna may respond, in particular in terms of phenology, remains poorly understood. The aim of this study was to assess how elevation could modify the relationships between climate variability (air temperature and snow melt‐out date), the timing of plant phenology and egg‐laying date of the coal tit (Periparus ater). We collected 9 years (2011–2019) of data on egg‐laying date, spring air temperature, snow melt‐out date, and larch budburst date at two elevations (~1,300 m and ~1,900 m asl) on a slope located in the Mont‐Blanc Massif in the French Alps. We found that at low elevation, larch budburst date had a direct influence on egg‐laying date, while at high‐altitude snow melt‐out date was the limiting factor. At both elevations, air temperature had a similar effect on egg‐laying date, but was a poorer predictor than larch budburst or snowmelt date. Our results shed light on proximate drivers of breeding phenology responses to interannual climate variability in mountain areas and suggest that factors directly influencing species phenology vary at different elevations. Predicting the future responses of species in a climate change context will require testing the transferability of models and accounting for nonstationary relationships between environmental predictors and the timing of phenological events.     

A model approach to project the start of egg laying of Great Tit (Parus major L.) in response to climate change

The aim of this study was to select a phenological model that is able to calculate the beginning of egg laying of Great Tit (Parus major) for both current and future climate conditions. Four models (M1–M4) were optimised on long-term phenological observations from the Ecological Research Centre Schlüchtern (Hessen/Germany). Model M1 was a common thermal time model that accumulates growing degree days (GDD) on an optimised starting date t ₁. Since egg laying of Great Tit is influenced not only by air temperature but also by photoperiod, model M1 was extended by a daylength term to give M2. The other two models, M3 and M4, correspond to M1 and M2, but t ₁ was intentionally set to 1 January, in order to consider already rising temperatures at the beginning of the year. A comparison of the four models led to following results: model M1 had a relatively high root mean square error at verification (RMSE_ver) of more than 4 days and can be used only to calculate the start of egg laying for current climate conditions because of the relatively late starting date for GDD calculation. The model failed completely if the starting date was set to 1 January (M3). Consideration of a daylength term in models M2 and M4 improved the performance of both models strongly (RMSE_ver of only 3 days or less), increased the credibility of parameter estimation, and was a precondition to calculate reliable projections in the timing of egg laying in birds for the future. These results confirm that the start of egg laying of Great Tit is influenced not only by air temperature, but also by photoperiod. Although models M2 and M4 both provide comparably good results for current climate conditions, we recommend model M4–with a starting date of temperature accumulation on 1 January–for calculating possible future shifts in the commencement of egg laying. Our regional projections in the start of egg laying, based on five regional climate models (RCMs: REMO-UBA, ECHAM5-CLM, HadCM3-CLM, WETTREG-0, WETTREG-1, GHG emission scenario A1B), indicate that in the near future (2011–2040) no significant change will take place. However, in the mid- (2041–2070) and long-term (2071–2100) range the beginning of egg laying could be advanced significantly by up to 11 days on average of all five RCMs. This result corresponds to the already observed shift in the timing of egg laying by about 1 week, due mainly to an abrupt increase in air temperature at the end of the 1980s by 1.2 K between April and May. The use of five regional climate scenarios additionally allowed to estimate uncertainties among the RCMs.     

Long-term trends in first arrival and first egg laying dates of some migrant and resident bird species in northern Italy

Climate change is affecting the phenology of seasonal events in Europe and the Northern Hemisphere, as shown by several studies of birds’ timing of migration and reproduction. Here, we analyse the long-term (1982–2006) trends of first arrival dates of four long-distance migratory birds [swift (Apus apus), nightingale (Luscinia megarhynchos), barn swallow (Hirundo rustica), and house martin (Delichon urbicum)] and first egg laying dates of two migrant (swift, barn swallow) and two resident species [starling (Sturnus vulgaris), Italian sparrow (Passer italiae)] at a study site in northern Italy. We also addressed the effects of local weather (temperature and precipitation) and a climate index (the North Atlantic Oscillation, NAO) on the interannual variability of phenological events. We found that the swift and the barn swallow significantly advanced both arrival and laying dates, whereas all other species did not show any significant temporal trend in either arrival or laying date. The earlier arrival of swifts was explained by increasing local temperatures in April, whereas this was not the case for arrival dates of swallows and first egg laying dates of both species. In addition, arrival dates of house martins were earlier following high NAO winters, while nightingale arrival was earlier when local spring rainfall was greater. Finally, Italian sparrow onset of reproduction was anticipated by greater spring rainfall, but delayed by high spring NAO anomalies, and swift’s onset of reproduction was anticipated by abundant rainfall prior to reproduction. There were no significant temporal trends in the interval between onset of laying and arrival in either the swift or the barn swallow. Our findings therefore indicate that birds may show idiosyncratic responses to climate variability at different spatial scales, though some species may be adjusting their calendar to rapidly changing climatic conditions.     

Pre-incubation feeding activities and energy budgets of Snow Geese: can food on the breeding grounds influence fecundity?

The potential contribution of early spring feeding conditions in the Arctic to clutch size variation was examined in a population of Lesser Snow Geese Anser caerulescens caerulescens. Behavioural observations were combined with energetic analyses of food material to derive an estimate of the energy budgets of pre-laying and laying females. Food intake of females between arrival on the breeding grounds and incubation was considerable; estimated energy gains in this period were in the same magnitude as the cost of one or several eggs. The pre-laying period spent on the breeding grounds can thus be energetically beneficial rather than costly. Accumulation of resources for reproduction in Snow Geese is a continual process including the breeding grounds, and nutrient limitation after arrival in the Arctic cannot sufficiently explain the environmental component of clutch size variation. The timing of migration and follicle development is such that clutch size decisions are sometimes made during the late stages of migration and some-times after arrival. In the latter case food conditions on the breeding grounds may greatly influence clutch size; in the former case they may still influence readjustments of clutch size after the initial decision. The universal negative correlation between clutch size and laying date in Snow Geese can be explained by negative fitness consequences of late hatching, which outweigh the benefits of delayed laying and further nutrient accumulation. Food shortage on the breeding grounds may sometimes be a secondary factor contributing to seasonal clutch size decline.     

Pathogenic bacteria and timing of laying

Pathogenic bacteria constitute a serious threat to viability of many organisms. Because growth of most bacteria is favored by humid and warm environmental conditions, earlier reproducers in seasonal environments should suffer less from the negative consequences of pathogenic bacteria. These relationships, and the effects on reproductive success, should be particularly prominent in predators because they are frequently exposed to pathogenic microorganisms from sick prey. Here, we presented and tested this hypothesis by sampling bacteria on adult and nestling goshawks Accipiter gentilis. We predicted that early breeders and their offspring should have fewer bacteria than those reproducing later during the breeding season. Adult goshawks with a high abundance of Staphylococcus on their beak and claws were easier to capture and their laying date was delayed. Moreover, goshawks that laid their eggs later had offspring with more Staphylococcus on their beaks and claws. The strength of the association between laying date and bacterial density of nestlings was stronger during the warm spring of 2013, when nestlings suffered from a higher abundance of pathogenic bacteria. Hatching failure and fledging failure were more common in nests with a higher abundance of Staphylococcus independently of the number of years occupied, laying date, and age of the female nest owner. These findings imply that timing of reproduction may be under the influence of pathogenic bacteria. Because early breeding goshawks produce more recruits than later breeders, our results suggest a role for pathogenic bacteria in the optimal timing of reproduction.     

Life cycle and growth ofTrichostegia minor (Curtis) in temporary woodland pools (Trichoptera: Phryganeidae)

Larvae of the caddisTrichostegia minor (Curtis) were collected from four woodland pools in The Netherlands, three of which are temporary, from August 1986 till June 1987. Eggs and larvae of this species proved to be very well adapted to drought, freezing, strongly fluctuating pH and alkalinity levels and prolonged oxygen deficit. The life cycle ofT.minor in a small woodland marsh overgrown byCalla palustris took one year. Adult flight period started at the end of May. Oviposition took place independent of water. Hatching of the eggs started in September and was probably induced by immersion. During the larval stage from September until May, 5 instars could be distinguished by the size of the head capsule. Growth of instars I, II and III during autumn was moderate. Most larvae overwintered as instar III or IV. Possibly there was a larval diapause during winter. In spring rapid growth to instar V took place prior to pupation. Growth rate, expressed as the increase of mean individual dry weight was highest from March to April (2.05±0.75% DW.m^–2.d^–1). In extremely shallow water growth in spring was initially more rapid compared to growth in deeper water. During winter the growth rate decreased to 0.038±0.071% DW.m^–2.d^–1. Net annual production based on the changes of momentary biomass was 183.2±31.7 mg DW.m^–2.y^–1 or 177.2±31.3 mg AFDW.m^–2.y^–1. Production loss during the winter season was 75.1±10.8 mg DW.m^–2.y^–1 or 72.3±10.6 mg AFDW.m^–2.y^–1.     

Experimentally induced clutch size enlargements affect reproductive success in the Pied Flycatcher

We performed a food provisioning experiment in a population of Pied Flycatchers Ficedula hypoleuca breeding at high altitude in central Spain to test if food availability before and during laying determines clutch size. Food was provided to one of two pairs with the same date of initiation of nest-building (15 dyads of subsequently reproducing pairs were thus created). Food provisioning began on the day of initiation of nest-building and ended on the day after the last egg was laid. Although laying date was unaffected by the experiment, clutch size in the experimental treatment was significantly larger. This result could indicate that food availability at laying (1) proximately constrained clutch size or (2) that females evaluated future conditions for incubating eggs and feeding nestlings based on food availability at laying. Reproductive success (proportion of eggs that resulted in fledged young) was significantly reduced in the experimental treatment. This effect suggest that supplemented females were tricked by the experiment into laying more eggs than the number of eggs they were able to incubate with success and the number of nestlings they were able to feed, a source of error in clutch size adjustment which could be common in non-experimental situations.     

Plasticity in laying dates of Canada Geese in response to spring phenology

Observed phenological changes can be explained either by individual phenotypic plasticity or by evolutionary changes, but there is more evidence pointing towards phenotypic plasticity to explain the mechanism behind changes in bird phenology. However, most studies on phenology have been conducted on insectivorous bird species for which breeding is closely tied to temperature and insect emergence. In this study, we examined the consequences of climatic conditions on the nesting phenology of temperate breeding Canada Geese Branta canadensis maxima, which rely on a continuous food supply, during a 14‐year period (2003–16). We determined whether laying dates were plastically adjusted to spring environmental conditions, and whether this adjustment resulted in a laying date advancement. We further estimated the strength and shape of selection acting on breeding timing, by looking at the effect of laying date on the relative number of young successfully hatched in a nest. We found that Geese plastically adjusted their laying date to spring maximum temperature (and not to precipitation or ice break‐up), resulting in a 9‐day advancement of laying date in the population for that period. Laying date was also moderately repeatable (r = 0.23) and subject to directional selection, but stabilizing selection was negligible. We thus demonstrate how Canada Geese plastically adjust laying dates to temperature, which may further be beneficial to nesting success. Evolutionary change of laying date to selection related to climate change, however, is still possible.     

Phenology model from surface meteorology does not capture satellite-based greenup estimations

Seasonal temperature change in temperate forests is known to trigger the start of spring growth, and both interannual and spatial variations in spring onset have been tied to climatic variability. Satellite dates are increasingly being used in phenology studies, but to date that has been little effort to link remotely sensed phenology to surface climate records. In this research, we use a two‐parameter spring warming phenology model to explore the relationship between climate and satellite‐based phenology. We employ daily air temperature records between 2000 and 2005 for 171 National Oceanographic and Atmospheric Administration weather stations located throughout New England to construct spring warming models predicting the onset of spring, as defined by the date of half‐maximum greenness (D₅₀) in deciduous forests as detected from Moderate Resolution Imaging Spectrometer. The best spring warming model starts accumulating temperatures after March 20th and when average daily temperatures exceed 5°C. The accumulated heat sums [heating degree day (HDD)] required to reach D₅₀ range from 150 to 300 degree days over New England, with the highest requirements to the south and in coastal regions. We test the ability of the spring warming model to predict phenology against a null photoperiod model (average date of onset). The spring warming model offers little improvement on the null model when predicting D₅₀. Differences between the efficacies of the two models are expressed as the ‘climate sensitivity ratio’ (CSR), which displays coherent spatial patterns. Our results suggest that northern (beech‐maple‐birch) and central (oak‐hickory) hardwood forests respond to climate differently, particularly with disparate requirements for the minimum temperature necessary to begin spring growth (3 and 6°C, respectively). We conclude that spatial location and species composition are critical factors for predicting the phenological response to climate change: satellite observations cannot be linked directly to temperature variability if species or community compositions are unknown.