Habitat Phenology Research Articles

Impacts of climate‐driven changes in habitat phenology on dynamics of niche overlaps and spatial associations in a boreal waterbird community

A fundamental, yet little‐explored, question is if climate change has affected niche relationships and spatial associations of native non‐invasive species in established local communities, potentially affecting interspecific interactions and community organization. Here, long‐term (1991‒2020) changes in habitat niche overlaps (HNOs; measured in terms of three habitat categories describing the amount and development of shore vegetation and shore depth) and spatial associations (SAs; measured as co‐occurrence on lakes) were studied in relation to climate‐driven changes in habitat phenology in a community of eight migratory waterbird species breeding on 37 lakes in southeastern Finland. Overall timing of ice‐out date (IOD) and within‐season variation in the timing of ice‐out (standard deviation of IOD, SDIOD) in lakes determine habitat (lake) availability for waterbirds during the settling phase. Previous work has documented that IOD has advanced and SDIOD increased during 1991‒2020, with species responding differently to these changes in their habitat use. HNO and SA varied considerably in the 28 species pairs of eight species during the study period. The effect of IOD and SDIOD on that variation was generally small, effect sizes differing from zero only in eight out of 112 cases. However, the direction and magnitude of the effects of IOD and SDIOD on HNO and SA varied considerably among the species pairs. Although not statistically significant, overall differences in the direction and magnitude of the effect sizes suggested that the impacts of IOD and SDIOD on HNO and SA were stronger in species pairs in which the species were more similar in terms of settling phenology, and stronger for early settling species than for late settling species. Observed changes in niche relationships probably reflect changes in interspecific interactions and affect the possibilities for heterospecific information use in habitat selection.

A green wave of saltmarsh productivity predicts the timing of the annual cycle in a long-distance migratory shorebird

Understanding how migratory animals respond to spatial and temporal variation in habitat phenology is critical for identifying selection pressures and tradeoffs at different life history stages. We examined the influence of breeding habitat phenology on life history timing of the eastern willet (Tringa semipalmata semipalmata) across a latitudinal gradient of breeding sites on the east coast of North America. To describe migration and life history timing, we deployed light-level geolocators on willets at breeding sites in New Jersey, Massachusetts and Maine, USA and evaluated additional data on life history timing and migratory connectivity from previous studies, eBird and band recoveries. Willets from Nova Scotia to Georgia winter exclusively on the Atlantic coast of northern South America and share common stopover sites. The timing of wintering site departure, breeding site arrival, nesting and southbound departure was later for birds breeding at higher latitudes while the duration of all life phases was similar across sites. Regardless of latitude, nesting corresponded with a consistent stage of seasonal salt marsh biomass accumulation and with peak spring temperature acceleration (GDD jerk). Temperature acceleration and salt marsh biomass were closely correlated with each other across the 11° latitudinal gradient we examined and with the timing of nest initiation across the northern 6° of this gradient. For this northern 6° of latitude, these results suggest that the timing of migration and breeding events in the annual cycle of eastern willets is constrained by a phenological “green wave” of spring salt marsh productivity at breeding sites.

Highly mobile insectivorous swifts perform multiple intra‐tropical migrations to exploit an asynchronous African phenology

With timely allocated movement phases, mobile organisms can match their space‐use with the seasonality of the environment and thereby optimise their resource utilisation over time. Long‐distance avian migrants are known to move with the seasonal dynamics on an annual basis, but how individuals respond to seasonality within their tropical non‐breeding range has been less studied. Here we analyse the movement pattern of a highly mobile aerial insectivorous bird, the pallid swift Apus pallidus, and its association with the local habitat phenology during the non‐breeding period, using individual‐based light‐level geolocation. We extracted timing and location of 21 birds’ residence periods, as well as characteristics of the intervening movements, such as distance and speed. We used time series of precipitation and vegetation data for each residence area to extract the timing of the local end of the rainy season and the onset of the dry season. The pallid swifts repeatedly upgraded their habitat by undertaking 2–5 intra‐tropical migrations correlated with the withdrawal of the rains and the onset of the local dry season. The birds arrived to the sites on average 12 days after rains ended and departed about two weeks after the onset of dry season suggesting that the birds closely tracked a spatiotemporal window presumably timed with optimal foraging conditions. Our results provide insights in the ways Palaearctic–African migrants respond to the asynchronous phenology within their sub‐Saharan non‐breeding range. We confirmed that pallid swifts actively respond to deteriorating conditions by repeated upgrades in habitat quality, which likely have substantial consequences for an individual's access to an essential, spatiotemporally ephemeral food resource. However, the pallid swifts did not surf an apparent resource wave per se as would be expected in a highly mobile species, indicating that also other factors, such as spatial patchiness of resources, may influence the movement decision.

Cascading climate effects and related ecological consequences during past centuries

Abstract. The interface between climate and ecosystem structure and function is incompletely understood, partly because few ecological records start before the recent warming phase. Here, we analyse an exceptional 100-yr long record of the great tit (Parus major) population in Switzerland in relation to climate and habitat phenology. Using structural equation analysis, we demonstrate an uninterrupted cascade of significant influences of the large-scale atmospheric circulation (North-Atlantic Oscillation, NAO, and North-sea – Caspian Pattern, NCP) on habitat and breeding phenology, and further on fitness-relevant life history traits within great tit populations. We then apply the relationships of this analysis to reconstruct the circulation-driven component of fluctuations in great tit breeding phenology and productivity on the basis of new seasonal NAO and NCP indices back to 1500 AD. According to the structural equation model, the multi-decadal oscillation of the atmospheric circulation likely led to substantial variation in habitat phenology, productivity and consequently, tit population fluctuations with minima during the "Maunder Minimum" (∼ 1650–1720) and the Little Ice Age Type Event I (1810–1850). The warming since 1975 was not only related with a quick shift towards earlier breeding, but also with the highest productivity since 1500, and thus, the impact of the NAO and NCP has contributed to an unprecedented increase of the population. A verification of the structural equation model against two independent data series (1970–2000 and 1750–1900) corroborates that the retrospective model reliably depicts the major long-term NAO/NCP impact on ecosystem parameters. The results suggest a complex cascade of climate effects beginning at a global scale and ending at the level of individual life histories. This sheds light on how large-scale climate conditions substantially affect major life history parameters within a population, and thus influence key ecosystem parameters at the scale of centuries.