Climate change and nesting behaviour in vertebrates: a review of the ecological threats and potential for adaptive responses

Nest building is a taxonomically widespread and diverse trait that allows animals to alter local environments to create optimal conditions for offspring development. However, there is growing evidence that climate change is adversely affecting nest‐building in animals directly, for example via sea‐level rises that flood nests, reduced availability of building materials, and suboptimal sex allocation in species exhibiting temperature‐dependent sex determination. Climate change is also affecting nesting species indirectly, via range shifts into suboptimal nesting areas, reduced quality of nest‐building environments, and changes in interactions with nest predators and parasites. The ability of animals to adapt to sustained and rapid environmental change is crucial for the long‐term persistence of many species. Many animals are known to be capable of adjusting nesting behaviour adaptively across environmental gradients and in line with seasonal changes, and this existing plasticity potentially facilitates adaptation to anthropogenic climate change. However, whilst alterations in nesting phenology, site selection and design may facilitate short‐term adaptations, the ability of nest‐building animals to adapt over longer timescales is likely to be influenced by the heritable basis of such behaviour. We urgently need to understand how the behaviour and ecology of nest‐building in animals is affected by climate change, and particularly how altered patterns of nesting behaviour affect individual fitness and population persistence. We begin our review by summarising how predictable variation in environmental conditions influences nest‐building animals, before highlighting the ecological threats facing nest‐building animals experiencing anthropogenic climate change and examining the potential for changes in nest location and/or design to provide adaptive short‐ and long‐term responses to changing environmental conditions. We end by identifying areas that we believe warrant the most urgent attention for further research.     

Arrival and onset of breeding of three passerine birds in eastern Finland tracks climatic variation and phenology of insects

Anthropogenic climate change poses a challenge to the annual cycles of migratory birds. It has become urgent to understand whether migratory birds are able to advance their spring phenology when the climate is warming and whether they are able to adjust these phenological phases to the spring phenology in their breeding areas. In this work, we studied long‐term trends in first arrival and onset of breeding for three passerine birds in eastern Finland; the pied flycatcher Ficedula hypoleuca, the common redstart Phoenicurus phoenicurus and the great tit Parus major. The pied flycatcher and the common redstart are long‐distance migrants while the great tit is a partial migrant in Finland. We asked what environmental variables best explain the first arrival or onset of breeding, if there is evidence of ‘thermal delay’ (long‐term increase in the accumulated temperatures) at arrival or onset of breeding and if the interannual variation in the onset of breeding correlates with variation in spring phenology of local insects. We found that the pied flycatcher and the common redstart had advanced their first arrival (explained by increased temperatures at the migration route), but we found no long‐term change in the onset of breeding (explained by local temperatures). Also, the onset of breeding of the great tit is tracking local temperatures. We found no or only weak evidence of thermal delay at arrival or onset of breeding for any of the species. The onsets of breeding for the pied flycatcher and the great tit are also closely tracking the spring phenology of the local insects. The stable or increasing population sizes of all three species in Finland could be a result from their ability to effectively track climatic and environmental variation.     

Phenological responses in a sycamore–aphid–parasitoid system and consequences for aphid population dynamics: A 20 year case study

Species interactions have a spatiotemporal component driven by environmental cues, which if altered by climate change can drive shifts in community dynamics. There is insufficient understanding of the precise time windows during which inter‐annual variation in weather drives phenological shifts and the consequences for mismatches between interacting species and resultant population dynamics—particularly for insects. We use a 20 year study on a tri‐trophic system: sycamore Acer pseudoplatanus, two associated aphid species Drepanosiphum platanoidis and Periphyllus testudinaceus and their hymenopteran parasitoids. Using a sliding window approach, we assess climatic drivers of phenology in all three trophic levels. We quantify the magnitude of resultant trophic mismatches between aphids and their plant hosts and parasitoids, and then model the impacts of these mismatches, direct weather effects and density dependence on local‐scale aphid population dynamics. Warmer temperatures in mid‐March to late‐April were associated with advanced sycamore budburst, parasitoid attack and (marginally) D. platanoidis emergence. The precise time window during which spring weather advances phenology varies considerably across each species. Crucially, warmer temperatures in late winter delayed the emergence of both aphid species. Seasonal variation in warming rates thus generates marked shifts in the relative timing of spring events across trophic levels and mismatches in the phenology of interacting species. Despite this, we found no evidence that aphid population growth rates were adversely impacted by the magnitude of mismatch with their host plants or parasitoids, or direct impacts of temperature and precipitation. Strong density dependence effects occurred in both aphid species and probably buffered populations, through density‐dependent compensation, from adverse impacts of the marked inter‐annual climatic variation that occurred during the study period. These findings explain the resilience of aphid populations to climate change and uncover a key mechanism, warmer winter temperatures delaying insect phenology, by which climate change drives asynchronous shifts between interacting species.     

Small changes in timing of breeding among subarctic passerines over a 32‐year period

Many bird populations in temperate regions have advanced their timing of breeding in response to a warming climate in recent decades. However, long‐term trends in temperature differ geographically and between seasons, and so do responses of local breeding populations. Data on breeding bird phenology from subarctic and arctic passerine populations are scarce, and relatively little data has been recorded in open‐nesting species. We investigated the timing of breeding and its relationship to spring temperature of 14 mainly open‐nesting passerine species in subarctic Swedish Lapland over a period of 32 years (1984–2015). We estimated timing of breeding from the progress of post‐juvenile moult in mist‐netted birds, a new method exploring the fact that the progress of post‐juvenile moult correlates with age. Although there was a numerical tendency for earlier breeding in most species (on average ?0.09 days/year), changes were statistically significant in only three species (by ?0.16 to ?0.23 days/year). These figures are relatively low compared with what has been found in other long‐term studies but are similar to a few other studies in subarctic areas. Generally, annual hatching dates were negatively correlated with mean temperature in May. This correlation was stronger in long‐distance than in short‐distance migrants. Although annual temperatures at high northern latitudes have increased over recent decades, there was no long‐term increase in mean temperature in May over the study period at this subarctic site. This is probably the main reason why there were only small long‐term changes in hatching dates.     

Tracking ice phenology by migratory waterbirds: settling phenology and breeding success of species with divergent population trends

Dependence on climate‐driven environmental cues in the initiation of life cycle stages is a critical attribute when assessing vulnerability of species to climate change impacts. This study focused on spring ice phenology as a cue to the settling of migratory waterbirds, asking whether there is an asynchrony between ice phenology and settling phenology that could affect breeding success of six species with divergent population trends. In the 37 study lakes in southeastern Finland, the ice‐out date not only varied considerably between years, but became progressively earlier during the study period, 1991–2018. Settling phenology of all species tracked inter‐annual variation in ice phenology. However, the degree of asynchrony between ice phenology and settling phenology varied between species, allowing discrimination between early and late settlers. Considerable inter‐annual variation also occurred within species, but in only one species did the degree of asynchrony correlate with the ice‐out date: for the horned grebe Podiceps auritus an earlier ice‐out date meant greater asynchrony between settling phenology and ice phenology. The degree of asynchrony between settling phenology and ice phenology did not affect breeding success in any species. However, ice phenology per se affected breeding success of horned grebes: earlier ice‐out was associated with lower annual breeding success. Breeding numbers of horned grebe showed a long‐term decline. Results suggest that short‐distance migratory birds are able to respond to climate change‐driven phenological changes in their breeding environments, and that this ability may not depend on the relative timing of breeding.     

Phenological advancement in arctic bird species: relative importance of snow melt and ecological factors

Previous studies have documented advancement in clutch initiation dates (CIDs) in response to climate change, most notably for temperate-breeding passerines. Despite accelerated climate change in the Arctic, few studies have examined nest phenology shifts in arctic breeding species. We investigated whether CIDs have advanced for the most abundant breeding shorebird and passerine species at a long-term monitoring site in arctic Alaska. We pooled data from three additional nearby sites to determine the explanatory power of snow melt and ecological variables (predator abundance, green-up) on changes in breeding phenology. As predicted, all species (semipalmated sandpiper, Calidris pusilla, pectoral sandpiper, Calidris melanotos, red-necked phalarope, Phalaropus lobatus, red phalarope, Phalaropus fulicarius, Lapland longspur, Calcarius lapponicus) exhibited advanced CIDs ranging from 0.40 to 0.80 days/year over 9 years. Timing of snow melt was the most important variable in explaining clutch initiation advancement (“climate/snow hypothesis”) for four of the five species, while green-up was a much less important explanatory factor. We found no evidence that high predator abundances led to earlier laying dates (“predator/re-nest hypothesis”). Our results support previous arctic studies in that climate change in the cryosphere will have a strong impact on nesting phenology although factors explaining changes in nest phenology are not necessarily uniform across the entire Arctic. Our results suggest some arctic-breeding shorebird and passerine species are altering their breeding phenology to initiate nesting earlier enabling them to, at least temporarily, avoid the negative consequences of a trophic mismatch.     

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to local adaptation. Thus, local adaptation and phenotypic plasticity among low and high elevation plant populations in response to climate, soil and other factors associated with elevational gradients might underlie different responses of these populations to climate warming. Using a transplant experiment along an elevational gradient, we investigated reproductive phenology, growth and reproduction of the nutrient‐poor grassland species Ranunculus bulbosus, Trifolium montanum and Briza media. Seeds were collected from low and high elevation source populations across the Swiss Alps and grown in nine common gardens at three different elevations with two different soil depths. Despite genetic differentiation in some traits, the results revealed no indication of local adaptation to the elevation of population origin. Reproductive phenology was advanced at lower elevation in low and high elevation populations of all three species. Growth and reproduction of T. montanum and B. media were hardly affected by garden elevation and soil depth. In R. bulbosus, however, growth decreased and reproductive investment increased at higher elevation. Furthermore, soil depth influenced growth and reproduction of low elevation R. bulbosus populations. We found no evidence for local adaptation to elevation of origin and hardly any differences in the responses of low and high elevation populations. However, the consistent advanced reproductive phenology observed in all three species shows that they have the potential to plastically respond to environmental variation. We conclude that populations might not be forced to migrate to higher elevations as a consequence of climate warming, as plasticity will buffer the detrimental effects of climate change in the three investigated nutrient‐poor grassland species.     

Herbarium records identify sensitivity of flowering phenology of eucalypts to climate: Implications for species response to climate change

Flowering phenology is very sensitive to climate and with increasing global warming the flowering time of plants is shifting to earlier or later dates. Changes in flowering times may affect species reproductive success, associated phenological events, species synchrony, and community composition. Long‐term data on phenological events can provide key insights into the impacts of climate on phenology. For Australia, however, limited data availability restricts our ability to assess the impacts of climate change on plant phenology. To address this limitation other data sources must be explored such as the use of herbarium specimens to conduct studies on flowering phenology. This study uses herbarium specimens for investigating the flowering phenology of five dominant and commercially important Eucalyptus species of south‐eastern Australia and the consequences of climate variability and change on flowering phenology. Relative to precipitation and air humidity, mean temperature of the preceding 3 months was the most influential factor on the flowering time for all species. In response to a temperature increment of 1°C, a shift in the timing of flowering of 14.1–14.9 days was predicted for E. microcarpa and E. tricarpa while delays in flowering of 11.3–15.5 days were found for E. obliqua, E. radiata and E. polyanthemos. Eucalyptus polyanthemos exhibited the greatest sensitivity to climatic variables. The study demonstrates that herbarium data can be used to detect climatic signals on flowering phenology for species with a long flowering duration, such as eucalypts. The robust relationship identified between temperature and flowering phenology indicates that shifts in flowering times will occur under predicted climate change which may affect reproductive success, fitness, plant communities and ecosystems.     

Climate warming: a loss of variation in populations can accompany reproductive shifts

The most documented response of organisms to climate warming is a change in the average timing of seasonal activities (phenology). Although we know that these average changes can differ among species and populations, we do not know whether climate warming impacts within‐population variation in phenology. Using data from five study sites collected during a 13‐year survey, we found that the increase in spring temperatures is associated with a reproductive advance of 10 days in natural populations of common lizards (Zootoca vivipara). Interestingly, we show a correlated loss of variation in reproductive dates within populations. As illustrated by a model, this shortening of the reproductive period can have significant negative effects on population dynamics. Consequently, we encourage tests in other species to assess the generality of decreased variation in phenological responses to climate change.     

Rapid genetic divergence in response to 15 years of simulated climate change

Genetic diversity may play an important role in allowing individual species to resist climate change, by permitting evolutionary responses. Our understanding of the potential for such responses to climate change remains limited, and very few experimental tests have been carried out within intact ecosystems. Here, we use amplified fragment length polymorphism (AFLP) data to assess genetic divergence and test for signatures of evolutionary change driven by long‐term simulated climate change applied to natural grassland at Buxton Climate Change Impacts Laboratory (BCCIL). Experimental climate treatments were applied to grassland plots for 15 years using a replicated and spatially blocked design and included warming, drought and precipitation treatments. We detected significant genetic differentiation between climate change treatments and control plots in two coexisting perennial plant study species (Festuca ovina and Plantago lanceolata). Outlier analyses revealed a consistent signature of selection associated with experimental climate treatments at individual AFLP loci in P. lanceolata, but not in F. ovina. Average background differentiation at putatively neutral AFLP loci was close to zero, and genomewide genetic structure was associated neither with species abundance changes (demography) nor with plant community‐level responses to long‐term climate treatments. Our results demonstrate genetic divergence in response to a suite of climatic environments in reproductively mature populations of two perennial plant species and are consistent with an evolutionary response to climatic selection in P. lanceolata. These genetic changes have occurred in parallel with impacts on plant community structure and may have contributed to the persistence of individual species through 15 years of simulated climate change at BCCIL.     

Population‐level thermal performance of a cold‐water ectotherm is linked to ontogeny and local environmental heterogeneity

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Influence of stochastic processes and catastrophic events on the reproductive dynamics of the endangered Maroon‐fronted Parrot Rhynchopsitta terrisi

Stochastic and catastrophic events may strongly impact the dynamics of wild populations. Annual fluctuations in rainfall may affect parrot populations, but few studies address the impact of other stochastic or catastrophic events on their population dynamics. The Maroon‐fronted Parrot Rhynchopsitta terrisi is an endangered species that nests colonially in cavities and crevices in limestone cliffs. From 1995 to 2010, we quantified Parrot attendance at nesting colonies throughout its breeding range, and reproductive output of nesting Parrots from 1997 to 2010 at the two most important nesting colonies. There was significant variation among colonies in the number of cavities occupied by Parrots each year. Rainfall significantly influenced both the number of occupied cavities and productivity, which declined after very dry years. Natural unpredictable events such as hurricanes did not modify the nesting activity of Maroon‐fronted Parrots at breeding colonies. However, wildfires increased in dry years, negatively affecting attendance at breeding colonies. The Maroon‐fronted Parrot may overcome the impacts of climatic variability, natural stochastic processes, and human‐induced catastrophic events by using nesting colonies as a network of resources throughout the breeding range. Given the current trends in climate change, it is likely the species may suffer stronger and more frequent unpredictable catastrophic events, potentially putting at risk its survival in the long term.     

Cascading reproductive isolation: Plant phenology drives temporal isolation among populations of a host‐specific herbivore

All organisms exist within a complex network of interacting species, thus evolutionary change may have reciprocal effects on multiple taxa. Here, we demonstrate “cascading reproductive isolation,” whereby ecological differences that reduce gene flow between populations at one trophic level affect reproductive isolation (RI) among interacting species at the next trophic level. Using a combination of field, laboratory and common‐garden studies and long‐term herbaria records, we estimate and evaluate the relative contribution of temporal RI to overall prezygotic RI between populations of Belonocnema treatae, a specialist gall‐forming wasp adapted to sister species of live oak (Quercus virginiana and Q. geminata). We link strong temporal RI between host‐associated insect populations to differences between host plant budbreak phenology. Budbreak initiates flowering and the production of new leaves, which are an ephemeral resource critical to insect reproduction. As flowering time is implicated in RI between plant species, budbreak acts as a “multitrophic multi‐effect trait,” whereby differences in budbreak phenology contribute to RI in plants and insects. These sister oak species share a diverse community of host‐specific gall‐formers and insect natural enemies similarly dependent on ephemeral plant tissues. Thus, our results set the stage for testing for parallelism in a role of plant phenology in driving temporal cascading RI across multiple species and trophic levels.     

Influence of experimental warming and shading on host–parasitoid synchrony

As the climate warms, many species are showing altered phenology patterns, potentially disrupting synchrony between interacting species. Recent studies have documented disrupted synchrony in plant–herbivore and predator–prey interactions. However, studies investigating climate‐related asynchrony in host–parasitoid interactions and exploring the relative responses of interacting hosts and parasitoids to climate change are lacking. This is an important gap in knowledge given the ubiquity of insect parasitoids and their importance in influencing the abundance and dynamics of their hosts. In the threatened marsh fritillary butterfly Euphydryas aurinia (Lepidoptera: Nymphalidae) and its specialized parasitoid, Cotesia bignellii (Hymenoptera: Braconidae) phenological synchrony (and consequently population fluctuations) are thought to be weather‐dependent. To assess the likely influence of climate and microenvironment change on synchrony between E. aurinia and C. bignellii, we experimentally manipulated the exposure of sensitive‐stage host larvae and parasitoid pupae to temperature (ambient or elevated) and shading (shaded or unshaded) regimes. We also analysed a 20‐year population dynamic dataset from the United Kingdom for E. aurinia to investigate whether population variations could be explained by interannual variations in the thermal and sunshine environment. Development times were affected significantly by the experimental temperature and shading treatments for E. aurinia but not for C. bignellii. However, the contrasting responses were insufficient to significantly affect host availability for parasitoids. In the field, thermal and sunshine conditions did not influence population fluctuations, and population variations across a large (UK‐wide) scale were uncorrelated. Changes to the thermal and sunshine environment of the magnitude investigated in our experiment and within the range experienced by wild E. aurinia populations over the last 20‐years thus seem unlikely to cause breakdown in host–parasitoid synchrony. We suggest that experiments investigating the mechanistic responses of interacting species to environmental change are needed to support the analysis and interpretation of observational data on species' phenology.     

A mineralogical record of ocean change: Decadal and centennial patterns in the California mussel

Ocean acidification, a product of increasing atmospheric carbon dioxide, may already have affected calcified organisms in the coastal zone, such as bivalves and other shellfish. Understanding species’ responses to climate change requires the context of long‐term dynamics. This can be particularly difficult given the longevity of many important species in contrast with the relatively rapid onset of environmental changes. Here, we present a unique archival dataset of mussel shells from a locale with recent environmental monitoring and historical climate reconstructions. We compare shell structure and composition in modern mussels, mussels from the 1970s, and mussel shells dating back to 1000–2420 years BP. Shell mineralogy has changed dramatically over the past 15 years, despite evidence for consistent mineral structure in the California mussel, Mytilus californianus, over the prior 2500 years. We present evidence for increased disorder in the calcium carbonate shells of mussels and greater variability between individuals. These changes in the last decade contrast markedly from a background of consistent shell mineralogy for centuries. Our results use an archival record of natural specimens to provide centennial‐scale context for altered minerology and variability in shell features as a response to acidification stress and illustrate the utility of long‐term studies and archival records in global change ecology. Increased variability between individuals is an emerging pattern in climate change responses, which may equally expose the vulnerability of organisms and the potential of populations for resilience.     

Forecasting range expansion into ecological traps: climate‐mediated shifts in sea turtle nesting beaches and human development

Some species are adapting to changing environments by expanding their geographic ranges. Understanding whether range shifts will be accompanied by increased exposure to other threats is crucial to predicting when and where new populations could successfully establish. If species overlap to a greater extent with human development under climate change, this could form ecological traps which are attractive to dispersing individuals, but the use of which substantially reduces fitness. Until recently, the core nesting range for the Critically Endangered Kemp's ridley sea turtle (Lepidochelys kempii) was ca. 1000 km of sparsely populated coastline in Tamaulipas, Mexico. Over the past twenty‐five years, this species has expanded its range into populated areas of coastal Florida (>1500 km outside the historical range), where nesting now occurs annually. Suitable Kemp's ridley nesting habitat has persisted for at least 140 000 years in the western Gulf of Mexico, and climate change models predict further nesting range expansion into the eastern Gulf of Mexico and northern Atlantic Ocean. Range expansion is 6–12% more likely to occur along uninhabited stretches of coastline than are current nesting beaches, suggesting that novel nesting areas will not be associated with high levels of anthropogenic disturbance. Although the high breeding‐site fidelity of some migratory species could limit adaptation to climate change, rapid population recovery following effective conservation measures may enhance opportunities for range expansion. Anticipating the interactive effects of past or contemporary conservation measures, climate change, and future human activities will help focus long‐term conservation strategies.     

Early springs and breeding performance in two sympatric duck species with different migration strategies

The capacity of migratory species to adapt to climate change may depend on their migratory and reproductive strategies. For example, reproductive output is likely to be influenced by how well migration and nesting are timed to temporal patterns of food abundance, or by temperature variations during the brood rearing phase. Based on two decades (1988–2009) of waterfowl counts from a boreal catchment in southern Finland we assessed how variation in ice break‐up date affected nesting phenology and breeding success in two sympatric duck species, Mallard Anas platyrhynchos and Eurasian Teal Anas crecca. In Fennoscandia these species have similar breeding habitat requirements but differ in migration distance; Teal migrate roughly seven times as far as do Mallard. Annual ice break‐up date was used as a proxy of spring ‘earliness’ to test the potential effect of climate change on hatching timing and breeding performance. Both species were capable of adapting their nesting phenology, and bred earlier in years when spring was early. However, the interval from ice break‐up to hatching tended to be longer in early springs in both species, so that broods hatched relatively later than in late springs. Ice break‐up date did not appear to influence annual number of broods per pair or annual mean brood size in either species. Our study therefore does not suggest that breeding performance in Teal and Mallard is negatively affected by advancement of ice break‐up at the population level. However, both species showed a within‐season decline in brood size with increasing interval between ice break‐up and hatching. Our study therefore highlights a disparity between individuals in their capacity to adjust to ice break‐up date, late breeders having a lower breeding success than early breeders. We speculate that breeding success of both species may therefore decline should a consistent trend towards earlier springs occur.     

Capturing Genetic Variation during Ecological Restorations: An Example from Kankakee Sands in Indiana

Genetic variation in populations, both natural and restored, is usually considered crucial for response to short‐term environmental stresses and for long‐term evolutionary change. To have the best chance of successful long‐term survival, restored populations should reflect the extant variation found in remnants, but restored sites may suffer from genetic bottlenecks as a result of founder effects. Kankakee Sands is a large‐scale restoration being conducted by The Nature Conservancy (TNC) in northwestern Indiana. Our goal was to test for loss of genetic variation in restored plant populations by comparing them with TNC’s seed source nursery and with local remnant populations that were the source of nursery seed and of the first few restored sites. Allozyme analysis of Baptisia leucantha, Asclepias incarnata, Coreopsis tripteris, and Zizia aurea showed low levels of allozyme diversity within all species and reductions in polymorphism, alleles per locus, and expected heterozygosity between remnants and restorations for all species except A. incarnata. Almost all lost alleles were rare; restored populations contained almost 90% of alleles at polymorphic loci that occurred in remnants at frequencies greater than 1%. Allele frequencies for most loci did not differ between remnants and restored sites. Most species showed significant allele frequency differentiation among remnant populations and among restored sites. Our results indicate that seed collection techniques used at Kankakee Sands captured the great majority of allozyme variation present in seed source remnant populations.     

Interannual bumble bee abundance is driven by indirect climate effects on floral resource phenology

Climate change can influence consumer populations both directly, by affecting survival and reproduction, and indirectly, by altering resources. However, little is known about the relative importance of direct and indirect effects, particularly for species important to ecosystem functioning, like pollinators. We used structural equation modelling to test the importance of direct and indirect (via floral resources) climate effects on the interannual abundance of three subalpine bumble bee species. In addition, we used long‐term data to examine how climate and floral resources have changed over time. Over 8 years, bee abundances were driven primarily by the indirect effects of climate on the temporal distribution of floral resources. Over 43 years, aspects of floral phenology changed in ways that indicate species‐specific effects on bees. Our study suggests that climate‐driven alterations in floral resource phenology can play a critical role in governing bee population responses to global change.     

Climate change and bird phenology: a long-term study in the Iberian Peninsula

Many studies in recent years have demonstrated long‐term temporal trends in biological parameters that can only be explained by climate change. Bird phenology has received great attention, as it studies one of the most conspicuous, popular, and easily observable phenomena in nature. There are many studies of long‐term changes in spring arrival dates, most of which concur with earlier records from the last few decades. However, few data are available for autumn departures or length of stays. Furthermore, existing data offer an equivocal picture. In this study, we analysed a huge database of about 44 000 records for five trans‐Saharan bird species (Ciconia ciconia, Cuculus canorus, Apus apus, Hirundo rustica and Luscinia megarhynchos). Data were collected from over 1300 sites around Spain during the period 1944–2004. Common spring arrival patterns were found in all species. Spring arrival dates have tended to advance since the mid‐1970s. Current dates are similar to those from the 1940s (except for C. ciconia). Thus, the advance of spring migration over the last three decades could be seen as a return to the initial timing of arrival dates, after abnormally delayed arrivals during the 1970s. A strong negative relationship with temperature in Spain at arrival time was observed in all species. A negative relationship with the Sahel Index (a measurement of precipitation in the African Sahel area during the rainy season) for the previous year was also found in C. canorus, A. apus and H. rustica. Regarding autumn departures, all species showed common interdecadal fluctuations, but only H. rustica is leaving earlier Spain at present. All species departed earlier in years that had higher temperatures during their reproductive period. However, only for H. rustica the relation between Spanish temperatures at departure time and the last sightings of individuals was significant. A heterogeneous temporal response for the length of stay was also found: C. ciconia increased, A. apus did not change and H. rustica decreased its stay. This is the first study, based on an extensive bird phenology observational network covering a large region, that shows the most complete and thorough analysis available for the Mediterranean region.