Influences of the El Niño/Southern Oscillation and the North Atlantic Oscillation on avian productivity in forests of the Pacific Northwest of North America

Abstract

To model the effects of global climate phenomena on avian population dynamics, we must identify and quantify the spatial and temporal relationships between climate, weather and bird populations. Previous studies show that in Europe, the North Atlantic Oscillation (NAO) influences winter and spring weather that in turn affects resident and migratory landbird species. Similarly, in North America, the El Niño/ Southern Oscillation (ENSO) of the Pacific Ocean reportedly drives weather patterns that affect prey availability and population dynamics of landbird species which winter in the Caribbean. Here we show that ENSO-and NAO-induced seasonal weather conditions differentially affect neotropicaland temperate-wintering landbird species that breed in Pacific North-west forests of North America. For neotropical species wintering in western Mexico, El Niño conditions correlate with cooler, wetter conditions prior to spring migration, and with high reproductive success the following summer. For temperate wintering species, springtime NAO indices correlate strongly with levels of forest defoliation by the larvae of two moth species and also with annual reproductive success, especially among species known to prey upon those larvae. Generalized linear models incorporating NAO indices and ENSO precipitation indices explain 50 -90% of the annual variation in productivity reported for 10 landbird species. These results represent an important step towards spatially explicit modelling of avian population dynamics at regional scales.

A multi‐isotope (δ2H, δ13C, δ15N) approach to establishing migratory connectivity of Barn Swallow (Hirundo rustica)

“…For example, we now suggest that the leapfrog migration hypothesis be tested using geolocators on southern vs. northern populations. Our identification of general regions of wintering for various breeding populations is also amenable to the testing of hypotheses associated with largescale environmental parameters such as those associated with climate (Sillett et al 2000, Nott et al 2002, LaManna et al 2012 or environmental conditions on the wintering grounds. For instance, future research could focus on testing whether patterns of population trends are associated with local rainfall and temperature parameters (Nott et al 2002, Ambrosini et al 2011b, LaManna et al 2012 or primary productivity in the wintering grounds measured by the Normalized Difference Vegetation Index (NDVI) (Ambrosini et al 2011a).…”

Persistent impacts of West Nile virus on North American bird populations

“…However, survival analyses examine the demographic parameter affected by WNV directly and therefore may provide a better assessment of potential impacts on bird populations. We developed models of annual survival over the 16-y period for each species or species group using latitude, longitude, and two climate indices, the El Niño-Southern Oscillation and the North Atlantic Oscillation, both known to influence avian reproduction (29) and survival (15) of North American landbirds. After leading regional and climatic models were identified, we tested 15 a priori hypotheses about the relationship between survival and WNV and land-use patterns (Table S2).…”

Cascading climate effects and related ecological consequences during past centuries

“…An effect of similar magnitude of the El Niño Southern Oscillation (ENSO) on the fecundity of black-throated blue warblers (Dendroica caerulescens) has been demonstrated by Sillett et al (2000). Also, Nott et al (2002) show impacts of the ENSO and the NAO on demographic parameters of several bird species within the late 20th century. Thus, the atmospheric oscillations may act similarly on many species in that they determine fundamental conditions at the scale of decades and operate at the top of cascades that include largescale weather conditions, local trophic webs and in turn, energetic conditions for reproduction.…”

“…4d) and demographic parameters (Fig. 4e) indicates that this plasticity cannot fully mitigate climate forcing on reproductive performance and thus, population persistence in various species (see also Nott et al, 2002;Both et al, 2004). The analysis of climate -ecology relationships over the past half millennium suggests that the recent changes in European woodland habitats and related trends in bird populations exceed the range of variation in the past.…”