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Shift to Later Timing by Autumnal Migrating Sharp-shinned Hawks
Abstract and Figures
Increasing proportions of Sharpshinned Hawks (Accipiter striatus) migrated later in autumn at the Hawk Ridge Bird Observatory, Duluth, Minnesota during 1974–2009. Migration averaged about 4 days later over 35 years since 1974, and about 8 days later during late September through October in the last 16 years of the study. Our results augment previous findings demonstrating recent shifts in phenological events for birds. The proximate causes and potential consequences of this later timing of migration should be investigated.
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... Systematic counts of migrating raptor numbers at Hawk Ridge, Duluth, Minnesota, USA, have been collected since 1972. Autumn migration phenology analyses have been done on this data set using a single species (Rosenfield et al. 2011), across species at Hawk Ridge (Van Buskirk 2012), and as a part of a larger study with other migration sites (Therrien et al. 2017). These studies have primarily found delays in autumn migration. ...
... Systematic hawk counts began at Hawk Ridge in 1972 and are now managed by Hawk Ridge Bird Observatory (HRBO) (Hofslund 1966, Peterson et al. 2015. Effort was not consistent in the first two years of the count (Rosenfield et al. 2011), but from 1974-1990 raptors were counted daily from 15 August to 31 October. To better count late migrating species, the count was extended into November in the early 1990s, and in 1997, was standardized to end on November 30. ...
... Statistical Analysis. Following Rosenfield et al. (2011), we dropped the data from 1972 and 1973 from this analysis because of low and inconsistent count effort. Before analyzing migration phenology, we considered the dates between which the majority of the individuals of a species are counted at Hawk Ridge (the passage window). ...
Changes in autumn raptor migration phenology have been documented at hawk count sites across North America. Delays in autumn migration are the most common shift reported, but these changes vary by species. We examined autumn raptor phenology and changes in count effort for 14 raptor species over 46 yr at Hawk Ridge in Duluth, Minnesota, USA, using mean passage date. Among the 14 raptors, six species showed significant shifts in migration phenology; four toward later migration and two toward earlier migration. Our results suggest fewer species are shifting toward later phenology than previously reported at Hawk Ridge and that some previously reported changes in phenology may be explained by changes in survey effort. This study highlights the importance of controlling for count effort when analyzing migration phenology, emphasizing the need for consistent effort in the future.
... There are relatively few studies that have investigated the possible effects of climate change on higher-level avian consumers, including predatory hawks (Clutton-Brock & Sheldon, 2010;Lehikoinen et al., 2010Lehikoinen et al., , 2013. However, some recent studies on raptors have shown earlier spring migration (Jaffré et al., 2013;Lehikoinen et al., 2010;Sullivan, Flaspohler, Froese, & Ford, 2016), earlier hatching dates (Lehikoinen et al., 2013), and shifts to earlier (Filippi-Codaccioni, Moussus, Urcun, & Jiguet, 2010) and later timing of autumnal migrants (Rosenfield, Lamers, Evans, Evans, & Cava, 2011;Van Buskirk, 2012), with such seasonal shifts being consistent with compensatory response to global warming (Sullivan et al., 2016). Sullivan et al. (2016) recently demonstrated phenological shifts to earlier spring migration of several raptor species, including Cooper's Hawks during 1979-2012 in the Great Lakes region of North America, and they indicated that such shifts were consistent with decadal climatic oscillations and global climate change. ...
... Alternatively, it is possible that changes in timing of migration could produce maladapted individuals given a possible decoupling between migration (and breeding) schedule of hawks and the temporal variation in available prey (Lehikoinen et al., 2009;Rosenfield et al., 2011). ...
... We used simple linear regression to assess how Julian date for the 50th percentile (i.e., median) of the of the total number of nests with estimated hatching dates in each of 36 study years changed across time (i.e., to ascertain whether a statistically significant shift in hatching date per year had occurred following procedures in Rosenfield et al. (2011)). ...
Numerous studies have demonstrated earlier timing of spring migration and egg‐laying in small passerines, but documentation of such responses to recent climate change in the life histories of higher trophic feeding birds such as raptors is relatively scarce. Raptors may be particularly susceptible to possible adverse effects of climate change due to their longer generation turnover times and lower reproductive capacity, which could lead to population declines because of an inability to match reproductive timing with optimal brood rearing conditions. Conversely adaptively favorable outcomes due to the influence of changing climate may occur. In general, birds that seasonally nest earlier typically have higher reproductive output compared to conspecifics that nest later in the season. Given the strong seasonal decline in reproductive output, and the heritability of nesting phenology, it is possible that nesting seasons would (adaptively) advance over time. Recent climate warming may release prior ecological constraints on birds that depend on food availability at the time of egg production, as do various raptors including Cooper's Hawks (Accipiter cooperii). Under this scenario, productivity, especially clutch size, might increase because it is likely that this reproductive demographic may be the most immediate response to the earlier seasonal presence of food resources. We demonstrated a statistically significant shift of about 4–5 days to an earlier timing of egg‐hatching in spring across 36 years during 1980–2015 for a partially migratory population of Cooper's Hawks in Wisconsin, United States, which is consistent with a recent study that showed that Cooper's Hawks had advanced their timing of spring migration during 1979–2012. Both studies occurred in the Great Lakes region, an area that compared to global averages is experiencing earlier and increased warming particularly in the spring in Wisconsin. The nesting period did not lengthen. We suggest that the gradual shift of six consecutive generations of hawks was likely in response to recent climate change or warming. We did not detect any long‐term temporal change in average clutch or brood sizes. However, such indices of reproduction are among the highest known for the species and thus may be at their physio‐ecological maximum for this population. Our study population appears to show resilience to and does not appear to be adversely influenced by the recent rate of changing climate at this time.
... The majority of avian climate studies have focused on timing of spring migration and the initiation of breeding. The effect of climate change on autumn migration has generally received less attention, with a few notable exceptions (Jenni and Kéry 2003, Van Buskirk et al. 2009, Filippi-Codaccioni et al. 2010, Rosenfield et al. 2011. Autumn migration represents a significant portion of the annual cycle of avian migratory species and plays a large role in their annual survival (Sillett and Holmes 2002). ...
... Evolutionary pressure on energetic condition can be strong, but few studies have evaluated how condition is affected by changes in climate or phenology (Swanson et al. 1999). In eastern North America, autumn migration has become earlier among long-distance Neotropical migrants, but is later for short-distance temperate migrants (Van Buskirk et al. 2009, Rosenfield et al. 2011. In Europe, autumn migration has also advanced among long-distance migrants, while no change or later departures were meas ured in short-distance migrants or bird species with a variable number of broods (Jenni andKéry 2003, Filippi-Codaccioni et al. 2010). ...
... We hypothesized that changes over time in migration phenology would depend on migration distance, diet, or both. Specifically, we predicted that long-distance Neotropical migrants would migrate earlier or have no change, whereas short-distance temperate migrants would migrate later (Jenni and Kéry 2003, Van Buskirk et al. 2009, Rosenfield et al. 2011. Also, we predicted that climate effects on phenology would differ Downloaded by [Robert Miller] at 14:33 23 January 2015 dependent upon diet as weather should influence food availability differently. ...
Climate change is having a dramatic effect on many migratory species. Changes in climate may lead to changes in food availability or other proximate cues that affect migratory behavior. We used 13 years (2000–2012) of data on songbird banding and raptor migration counts and captures during autumn migration in the intermountain West to evaluate whether regional temperature or precipitation or hemispheric climate indices predicted autumn migratory timing and energetic condition. We examined overall trends and evaluated the effects of diet and migratory distance on phenology and conditional responses. For the 13-year study period, no temperature, precipitation, or climate index trends were evident. There was no change in migratory timing for all species combined, but trends were apparent when evaluated by diet and migratory distance. The magnitude of these changes varies by diet and by migratory distance, but not as predicted by previous research of autumn timing in other parts of the globe. Long-distance migrants tended to migrate later in autumn, whereas short-distance migrants exhibited no change in timing. Annual variation in timing was predicted by regional temperature and precipitation and by hemispheric climate indices, and the predicted effects differed by diet and migratory distance. Granivores responded to the broadest set of climate indices, whereas avivores responded to the least. Frugivores responded with the greatest magnitude to annual variation in climate. We did not measure food availability but in most cases the predictive effect of climate on migratory timing of birds was consistent with predicted effects on food. Frugivorous birds migrated earlier in warmer years when fruit quality and quantity were expected to be lower. Energetic condition measurements supported the food hypotheses in some, but not all cases. The different responses of species to annual variation in climate suggest that different species integrate difference cues in their decision to migrate.
... The original analysis of those data suggested migratory populations of golden eagles over much of the western United States have declined since the mid-1980s, and in particular from 1995 to 2005 . However, recent analyses suggest migratory behavior of some North American raptors may be changing in response to climate change (Rosenfield et al. 2011, Buskirk 2012, and we wanted to assess whether this might be a factor in the golden eagle trends reported by Farmer et al. (2008). In addition to providing insights into golden eagle population change over the analysis period, our results also extend the utility of the hierarchical model developed by Sauer and Link (2011) in generating estimates of population numbers through the incorporation of estimated detection probabilities from the WGES. ...
... We hypothesize that this pattern may be a consequence of changes in migratory behavior that result in fewer golden eagles arriving at southern hawk watch sites during the time those sites are operating. This could occur if fewer golden eagles left northern breeding areas, if they migrated shorter distances, or if migration were delayed in time, such as has been reported for the sharp-shinned hawk (Accipiter striatus; Rosenfield et al. 2011) and other raptors in eastern North America (Buskirk 2012). This hypothesis should be explored further with full data from these hawk watch sites. ...
... We suggest that the long history of counting concentrated waterbirds at WP and our data from KP support the opinion that Lake Superior can provide important new insights into the use of nearshore habitats by this group of birds and can also serve as a population index for long term monitoring. Similar data have been used to identify changes in the migratory timing of raptors consistent with climate change in the last 40 years (Rosenfield et al., 2011;Sullivan et al., 2015;Van Buskirk, 2012). This work from one season provides new insights into waterbird movement. ...
The Great Lakes are used as a migratory corridor and for feeding by tens of thousands of waterbirds each spring and fall, yet little species-specific information is available regarding numbers, seasonal timing, and connectivity along the route. The objective of this study was to use land-based surveys to quantify fall migration at two important landmarks in Lake Superior for an assemblage of waterbirds from three orders (Anseriformes, Gaviiformes, and Podicipediformes). Both the Keweenaw Peninsula (KP) and Whitefish Point (WP) showed a temporal pattern of high numbers (peaking at 9000 and 16,000, respectively) in the first 3 h after dawn and a decline (dropping to 1000 and 5000, respectively) over the following 5 h, although the decline was far more abrupt at KP than at WP. Fall totals for WP were nearly 85,000 individual waterbirds, and for KP about 34,500. Species abundance rank-ings were generally similar for both locations, with the most common species being long-tailed duck (Clangula hyemalis), red-necked grebe (Podiceps grisegena), greater scaup (Aythya marila), and red-breasted merganser (Mergus serrator). Most species were far more numerous at WP than at KP, with long-tailed ducks being 65 times more numerous. A notable exception was redhead (Aythya americana), which was 33% more numerous at KP than at WP. We suggest that during the fall, Lake Superior acts as a geographic funnel concentrating waterbirds from northwest to southeast and that details of the composition, timing and amplitude of this phenomenon are important considerations for any nearshore Great Lakes development.
... Such changes in mean arrival time may appear modest, yet the importance of phenological sychrony between predator and prey have been shown for some bird taxa (Strode 2003. We focus on spring arrivals, but multiple studies in North America and Europe have found that migratory birds of prey delay their fall depatures in a manner consistent with climate change (Rosenfield et al. 2011, Van Buskirk 2012, Jaffré et al. 2013) and may also be undergoing adaptive changes in nesting dates and migration distances (Heath et al. 2012). Lacking evidence that these behavioral responses are sufficent to maintain productivity, survivorship and competitive relationships, we believe such shifts are a cause for concern and a call for detailed studies such as ours in other parts of the world (Knudsen et al. 2011). ...
Many birds have advanced their spring migration and breeding phenology in response to climate change, yet some long-distance migrants appear constrained in their adjustments. In addition, bird species with long generation times and those in higher trophic positions may also be less able to track climate-induced shifts in food availability. Migratory birds of prey may therefore be particularly vulnerable to climate change because: 1) most are long-lived and have relatively low reproductive capacity, 2) many feed predominately on insectivorous passerines, and 3) several undertake annual migrations totaling tens of thousands of kilometers. Using multi-decadal datasets for 14 raptor species observed at six sites across the Great Lakes region of North America, we detected phenological shifts in spring migration consistent with decadal climatic oscillations and global climate change. While the North Atlantic and El Niño Southern Oscillations exerted heterogeneous effects on the phenology of a few species, arrival dates more generally advanced by 1.18 days per decade, a pattern consistent with the effects of global climate change. After accounting for heterogeneity across observation sites, five of the 10 most abundant species advanced the bulk of their spring migration phenology. Contrary to expectations, we found that long-distance migrants and birds with longer generation times tended to make the greatest advancements to their spring migration. Such results may indicate that phenotypic plasticity can facilitate climatic responses among these long-lived predators.This article is protected by copyright. All rights reserved.
... mate change already may be affecting distribution of Bald Eagles, both spatially and temporally, such that northern migrants may not move as far south as in prior years, potentially resulting in what appears to be a declining trend in the south, but increasing trend in the north (National Audubon Society 2014). Additionally, evidence that migration behavior may be changing, possibly due to climate change, has been documented for Bald Eagles (Buskirk 2012) and several other raptors as well (Rosenfield et al. 2011, Millsap et al. 2013. ...
We analyzed counts from the annual Midwinter Bald Eagle Survey to examine state, regional, and national trends in counts of wintering Bald Eagles (Haliaeetus leucocephalus) within the conterminous 48 United States from 1986 to 2010. Using hierarchical mixed model methods, we report trends in counts from 11 729 surveys along 844 routes in 44 states. Nationwide Bald Eagle counts increased 0.6% per yr over the 25-yr period, compared to an estimate of 1.9% per yr from 1986 to 2000. Trend estimates for Bald Eagles were significant (P ≤ 0.05) and positive in the northeastern and northwestern U.S. (3.9% and 1.1%, respectively), while trend estimates for Bald Eagles were negative (P ≤ 0.05) in the southwestern U.S. (−2.2%). After accounting for potential biases resulting from temporal and regional differences in surveys, we believe trends reflect post-DDT recovery and subsequent early effects of density-dependent population regulation.
... The best example may be the Sharp-shinned Hawk, which has been reported to short-stop in several articles (Viverette et al. 1994;Duncan 1996;Viverette et al. 1996;Chandler et al. 2004;McCarty and Bildstein 2005). However, a later study (Rosenfield et al. 2011) demonstrated that the autumn migration has merely been delayed, probably due to increasing numbers of bird feeders upstream in the flyway attracting passerines and other suitable prey for Sharp-shins, i.e. hawks were migrating less rapidly in response to increased prey availability, but not changing their ultimate wintering areas. ...
The term 'short-stopping' is increasingly used in ecology to describe spatio-temporal changes in occurrence of migratory species. Spurred by the insight that it has been used in a variety of contexts, we reviewed its use in avian ecology. A literature search yielded 59 papers explicitly treating short-stopping in birds, most of them in peer-reviewed journals. The term was first used in 1967 to describe a northward shift in wintering Canada Geese in North America and has been used with increasing frequency to the present day. Geese dominate the short-stopping literature, which is confined to the northern hemisphere. Short-stopping has been used to describe (1) a shortened autumn migration that results in a wintering distribution closer to breeding areas, (2) a shortened spring migration that results in a breeding distribution closer to wintering areas, and (3) a delay in autumn migration that leads to a perceived reduced abundance in some part of the winter range. We advocate that short-stopping should be used only to describe (1) range shifts that involve shortening of the migratory corridor, and that they are qualified explicitly by season (i.e. breeding/winter) and degree (i.e. full or partial range shift). In other cases of breeding, wintering or entire range shifts where the migratory corridor is elongated or remains the same, we recommend using the term 'range shift', qualified by season, geography and orientation (i.e. the direction of the range shift). We also discuss the need for spatially explicit avian count monitoring mechanisms (rather than capture-recapture or hunting bag data) designed specifically to track such changes in distribution in the future.
We examined banding encounter records from 1920 to 2006 for three raptors that are commonly banded in North America: American Kestrel (Falco sparverius, 4707 encounters), Sharp-shinned Hawk (Accipiter striatus; 5256), and Cooper's Hawk (A. cooperii; 3848). We selected birds banded during summer or autumn migration and encountered during winter to investigate movement distances and winter latitudes by sex, age, year banded, banding latitude, and flyway. Female American Kestrels migrated farther than males, but travel distances did not vary by age. Distance moved to wintering sites declined with encounter year for American Kestrels, suggesting that migratory short-stopping may be occurring across North America. Movements of the three species typically showed a chain migration pattern; however, female American Kestrels from the most northern latitudes demonstrated a leapfrog pattern, moving beyond mid-latitude birds to more southerly wintering latitudes. Female American Kestrels and Cooper's Hawks moved farther than males, whereas Sharp-shinned Hawk migration distances did not vary by sex. Hatch-year Sharp-shinned and Cooper's hawks moved farther than after-hatch-year birds, whereas no age difference was observed for American Kestrels. For all three species, northern-latitude birds moved farther than mid- or low-latitude birds, and low-latitude birds appeared to be largely resident. Distances moved also varied by flyway for both accipiters.
La forêt boréale se caractérise par une diversité de cycles de productivité qui affectent les chaînes trophiques, lesquelles sont en partie affectées par le climat. Nous avons analysé les données de l’Observatoire d’oiseaux de Tadoussac pour l’épervier brun ( Accipiter striatus ) entre 1996 et 2010 en lien avec l’indice climatique de l’Oscillation nord-atlantique (ONA), les précipitations estivales et l’abondance de proies potentielles. À l’automne, les éperviers bruns juvéniles ont migré plus tôt que les adultes et les déplacements des 2 groupes ne se sont pas chevauchés. L’abondance automnale de l’épervier brun, principalement celle des juvéniles, était positivement corrélée avec l’indice climatique de l’ONA de l’hiver précédent, et négativement avec les précipitions des mois de juin et juillet, lesquelles sont reliées à l’indice de l’ONA. De plus, nos résultats ont révélé des corrélations positives entre l’abondance de l’épervier brun lors de la migration d’automne et l’abondance de proies potentielles en période estivale, principalement celle de la grive à dos olive ( Catharus ustulatus ) et du junco ardoisé ( Junco hyemalis ). La corrélation positive entre l’abondance d’éperviers bruns et l’ONA de l’hiver précédent suggère que le climat influence probablement la dynamique de population de l’espèce. Les hivers doux et enneigés sont souvent suivis d’un été pluvieux, qui se caractérise par une production moindre de jeunes éperviers. Cela semble lié à la disponibilité de proies pour les éperviers adultes puisque les proies principales sont également moins nombreuses lors d’étés avec une pluviosité supérieure à la normale.
About 0.5 percent of all Sharp-shinned Hawks ringed at Duluth, Minnesota, on migration were recovered, showing that the winter distribution spanned about 35° of latitude, from central Wisconsin to Costa Rica. Females migrated before males of corresponding age, and wintered substantially further south.
Each fall, migrating Sharp-shinned Hawks (Accipiter striatus) are counted at traditional raptor-migration watch sites in eastern North America. During the 1980s and early 1990s, declines in the numbers of Sharp-shinned Hawks sighted at many of these sites raised concerns about the population status of the species. Using count data from Hawk Mountain Sanctuary, Pennsylvania, and Cape May Point, New Jersey, we offer additional evidence that the reported decline is greater at raptor-migration watch sites along the Atlantic coast than at sites farther inland. Band-recovery data for faU migrants indicate that Hawk Mountain Sanctuary and Cape May Point count birds that essentially are from the same eastern pop- ulation. An analysis of Christmas'"bird-count data for easternmost North America during the 1980s indicates significant increases in the numbers of Sharp-shinned Hawks observed north of the two sites. We suggest that at least part of the decline in numbers of Sharp-shinned Hawks sighted at traditional watch sites in eastern North America may result from migratory short stopping. Received 29 September 1994, accepted 18 March 1995. !
Past studies of bird migration times have shown great variation in migratory responses to climate change. We used 33 years of bird capture data (1970–2002) from Manomet, Massachusetts to examine variation in spring migration times for 32 species of North American passerines. We found that changes in first arrival dates – the unit of observation used in most studies of bird migration times – often differ dramatically from changes in the mean arrival date of the migration cohort as a whole. In our study, the earliest recorded springtime arrival date for each species occurred 0.20 days later each decade. In contrast, the mean arrival dates for birds of each species occurred 0.78 days earlier each decade. The difference in the two trends was largely explained by declining migration cohort sizes, a factor not examined in many previous studies. We found that changes in migration cohort or population sizes may account for a substantial amount of the variation in previously documented changes in migration times. After controlling for changes in migration cohort size, we found that climate variables, migration distance, and date of migration explained portions of the variation in migratory changes over time. In particular, short-distance migrants appeared to respond to changes in temperature, while mid-distance migrants responded particularly strongly to changes in the Southern Oscillation Index. The migration times of long-distance migrants tended not to change over time. Our findings suggest that previously reported changes in migration times may need to be reinterpreted to incorporate changes in migration cohort sizes.
Here we argue that features of migration such as timing and routing are strongly affected by safety
concerns, and that careful consideration of such can illuminate aspects of migratory ecology. Phenomena
such as bad weather may also threaten migrant safety, but our interest here is limited to predators. Our thesis is that both density-mediated and trait-mediated effects (see Lind and Cresswell 2005) have profound and pervasive influences on the evolution of avian migration, with the latter being especially significant. We consider a number of continental-scale migratory phenomena and explain how, in contrast to existing explanatory hypotheses, these can be viewed as tactics to increase safety.
Weather is of major importance for the population dynamics of birds, but the implications of climate change have only recently begun to be addressed. There is already compelling evidence that birds have been affected by recent climate changes. This review suggests that although there is a substantial body of evidence for changes in the phenology of birds, particularly of the timing of migration and of nesting, the consequences of these responses for a species’ population dynamics is still an area requiring in-depth research. The potential for phenological miscuing (responding inappropriately to climate change, including a lack of response) and for phenological disjunction (in which a bird species becomes out of synchrony with its environment) are beginning to be demonstrated, and are also important areas for further research. The study of climatically induced distributional change is currently at a predictive modelling stage, and will need to develop methods for testing these predictions. Overall, there is a range of intrinsic and extrinsic factors that could potentially inhibit adaptation to climate change and these are a high priority for research.
Climate change creates new challenges for biodiversity conservation. Species ranges and ecological dynamics are already responding to recent climate shifts, and current reserves will not continue to support all species they were designed to protect. These problems are exacerbated by other global changes. Scholarly articles recommending measures to adapt conservation to climate change have proliferated over the last 22 years. We systematically reviewed this literature to explore what potential solutions it has identified and what consensus and direction it provides to cope with climate change. Several consistent recommendations emerge for action at diverse spatial scales, requiring leadership by diverse actors. Broadly, adaptation requires improved regional institutional coordination, expanded spatial and temporal perspective, incorporation of climate change scenarios into all planning and action, and greater effort to address multiple threats and global change drivers simultaneously in ways that are responsive to and inclusive of human communities. However, in the case of many recommendations the how, by whom, and under what conditions they can be implemented is not specified. We synthesize recommendations with respect to three likely conservation pathways: regional planning; site-scale management; and modification of existing conservation plans. We identify major gaps, including the need for (1) more specific, operational examples of adaptation principles that are consistent with unavoidable uncertainty about the future; (2) a practical adaptation planning process to guide selection and integration of recommendations into existing policies and programs; and (3) greater integration of social science into an endeavor that, although dominated by ecology, increasingly recommends extension beyond reserves and into human-occupied landscapes.
The cues used by birds and other species to trigger reproduction determine how successfully they can respond to climate change.