Tracking multi-generational colonization of the breeding grounds by monarch butterflies in eastern North America

Insect migration may involve movements over multiple breeding generations at continental scales, resulting in formidable challenges to their conservation and management. Using distribution models generated from citizen scientist occurrence data and stable-carbon and -hydrogen isotope measurements, we tracked multi-generational colonization of the breeding grounds of monarch butterflies ( Danaus plexippus ) in eastern North America. We found that monarch breeding occurrence was best modelled with geographical and climatic variables resulting in an annual breeding distribution of greater than 12 million km 2 that encompassed 99% occurrence probability. Combining occurrence models with stable isotope measurements to estimate natal origin, we show that butterflies which overwintered in Mexico came from a wide breeding distribution, including southern portions of the range. There was a clear northward progression of monarchs over successive generations from May until August when reproductive butterflies began to change direction and moved south. Fifth-generation individuals breeding in Texas in the late summer/autumn tended to originate from northern breeding areas rather than regions further south. Although the Midwest was the most productive area during the breeding season, monarchs that re-colonized the Midwest were produced largely in Texas, suggesting that conserving breeding habitat in the Midwest alone is insufficient to ensure long-term persistence of the monarch butterfly population in eastern North America.

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Wing Color of Monarch Butterflies (Danaus plexippus) in Eastern North America across Life Stages: Migrants Are “Redder” than Breeding and Overwintering Stages

Psyche A Journal of Entomology ◽

10.1155/2009/705780 ◽

2009 ◽

Vol 2009 ◽

pp. 1-5 ◽

Cited By ~ 10

Author(s):

Andrew K. Davis

Keyword(s):

North America ◽

Southeastern United States ◽

Danaus Plexippus ◽

Color Difference ◽

Color Variation ◽

Eastern North America ◽

Life Stages ◽

Monarch Butterflies ◽

Bright Orange ◽

The Many

Monarch butterflies are famous among insects for their unique migration in eastern North America to overwinter sites in Mexico and their bright orange wing color, which has an aposematic function. While capturing migrating monarchs in northeast Georgia, USA, I noticed that many appeared to have unusually deep orange wings. I initiated the current study to compare wing hues (obtained using image analysis of scanned wings) of migrants (captured in 2005 and 2008) to samples of breeding and overwintering monarchs. Consistent with initial observations, migrants had significantly lower orange hues (reflecting deeper, redder orange colors) than breeding and overwintering monarchs. There was also a difference in hue between sexes and a relationship with wing size, such that larger monarchs had deeper, redder hues. The reasons for the color difference of migrants are not apparent, but one possibility is that the longer-lived migrant generation has denser scalation to allow for scale loss over their lifespan. Alternatively, this effect could be confined to the subpopulation of monarchs in the Southeastern United States, which may not be well represented at the Mexican overwintering sites. In any case, this discovery highlights the many questions emerging on the significance of wing color variation in this species.

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No broad decline of breeding monarch butterflies in North America: implications for conservation efforts

10.1101/2021.08.03.454948 ◽

2021 ◽

Author(s):

Andrew K Davis ◽

Michael S Crossley ◽

Matthew K Moran ◽

Jeffrey Glassberg ◽

William E Snyder

Keyword(s):

North America ◽

Habitat Restoration ◽

Danaus Plexippus ◽

Geographic Range ◽

Breeding Habitat ◽

Flagship Species ◽

Monarch Butterflies ◽

Breeding Populations ◽

First Time

Many insects are in clear decline, with monarch butterflies (Danaus plexippus) drawing particular attention as a flagship species. Falling numbers of overwintering monarchs are well documented, but there has been debate regarding population trends of summer breeding populations. Here, we compile a series of long-term monarch monitoring datasets, some which are analyzed here for the first time, that reveal highly variable responses across the migratory geographic range, but no broad net decline in numbers of breeding monarchs. We also did not find evidence that sampling biased towards natural sites was masking declines at disturbed sites. Overall, our results suggest a robust resiliency in summer populations that thus far has allowed recovery from losses during the winter. Thus, monarchs may not require as much breeding habitat restoration as once thought, and focus should be on conserving the fall and spring migration.

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Estimating the annual distribution of monarch butterflies in Canada over 16 years using citizen science data

FACETS ◽

10.1139/facets-2018-0011 ◽

2019 ◽

Vol 4 (1) ◽

pp. 238-253

Author(s):

D. T. Tyler Flockhart ◽

Maxim Larrivée ◽

Kathleen L. Prudic ◽

D. Ryan Norris

Keyword(s):

North America ◽

Citizen Science ◽

Habitat Restoration ◽

Danaus Plexippus ◽

The United States ◽

Science Data ◽

Eastern Canada ◽

Long Distance ◽

Monarch Butterflies ◽

Breeding Distribution

Monarch butterflies ( Danaus plexippus, Linnaeus, 1758) are comprised of two migratory populations separated by the Rocky Mountains and are renowned for their long-distance movements among the United States, Canada, and Mexico. Both populations have declined over several decades across North America prompting all three countries to evaluate conservation efforts. Monitoring monarch distribution and abundance is a necessary aspect of ongoing management in Canada where they are a species at risk. We used presence-only data from two citizen science data sets to estimate the annual breeding distribution of monarch butterflies in Canada between 2000 and 2015. Monarch breeding distribution in Canada varied widely among years owing to natural variation, and when considering the upper 95% of the probability of occurrence, the annual mean breeding distribution in Canada was 484 943 km2 (min: 173 449 km2; max: 1 425 835 km2). The area of occurrence was approximately an order of magnitude larger in eastern Canada than in western Canada. Habitat restoration for monarch butterflies in Canada should prioritize productive habitats in southern Ontario where monarchs occur annually and, therefore, likely contribute most to the long-term viability of monarchs in eastern North America. Overall, our assessment sets the geographic context to develop successful management strategies for monarchs in Canada.

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Factors influencing fall departure phenology in migratory birds that bred in northeastern North America

The Auk ◽

10.1093/auk/ukz064 ◽

2019 ◽

Author(s):

Émile Brisson-Curadeau ◽

Kyle H Elliott ◽

Pascal Côté

Keyword(s):

North America ◽

Short Distance ◽

Migratory Birds ◽

Breeding Habitat ◽

Temperature Changes ◽

Migration Timing ◽

Warm Weather ◽

Breeding Grounds ◽

Timing Of Migration ◽

Migrating Birds

Abstract The phenology of migrating birds is shifting with climate change. For instance, short-distance migrants wintering in temperate regions tend to delay their migration in fall during spells of warmer temperature. However, some species do not show strong shifts, and the factors determining which species will react to temperature changes by delaying their migration are poorly known. In addition, it is not known whether a slower migration or a postponed departure creates the observed delays in fall migration because most studies occur far south of the boreal breeding areas making it difficult to separate those 2 mechanisms. We used 22 yr of data at a northern observatory in eastern North America, at the southern edge of the boreal forest, to examine how 21 short-distance migrants responded to changing temperatures. We investigated if those species responding to temperature share life-history features (i.e. diet, size, total migration distance, breeding habitat, timing of migration). The period of migration in each species was, by far, the most important factor predicting the response of a species to temperature. Eight of the 13 species migrating in October changed their migration onset with temperature (usually by delaying migration by 1–2 days/°C), while the migration timing of none of the 8 species migrating in September was dependent on temperature. Furthermore, the absence of a greater migration delay by birds breeding farther from the study site (i.e. Arctic-breeding birds) suggests the mechanism is a postponed departure rather than a slower migration. We conclude that temperature variations in late fall influence the conditions on the breeding grounds, so that birds still present at that time benefit more from postponing their departure in warm weather.

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Do Barrow's Goldeneyes, Bucephala islandica, Breed South of the St. Lawrence Estuary in the Gaspé Peninsula, Eastern Canada?

The Canadian Field-Naturalist ◽

10.22621/cfn.v124i2.1057 ◽

2010 ◽

Vol 124 (2) ◽

pp. 179

Author(s):

Jean-François Ouellet ◽

Pierre Fradette ◽

Isabel Blouin

Keyword(s):

North America ◽

Breeding Season ◽

Breeding Habitat ◽

Eastern North America ◽

Eastern Canada ◽

Lawrence Estuary ◽

North Shore ◽

The North ◽

Bucephala Islandica ◽

St Lawrence Estuary

We report the first observations of Barrow's Goldeneyes south of the St. Lawrence estuary in typical breeding habitat during the breeding season. Until recently, the confirmed breeding locations for the species in Eastern North America were all located on the north shore of the Estuary and Gulf of St. Lawrence.

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A poor substitute for the real thing: captive-reared monarch butterflies are weaker, paler and have less elongated wings than wild migrants

Biology Letters ◽

10.1098/rsbl.2019.0922 ◽

2020 ◽

Vol 16 (4) ◽

pp. 20190922 ◽

Cited By ~ 3

Author(s):

Andrew K. Davis ◽

Farran M. Smith ◽

Ashley M. Ballew

Keyword(s):

Danaus Plexippus ◽

Late Summer ◽

Population Declines ◽

Average Strength ◽

Long Distance ◽

Monarch Butterflies ◽

Real Thing ◽

In The Wild ◽

Wild Group ◽

Migration Propensity

For many animals and insects that are experiencing dramatic population declines, the only recourse for conservationists is captive rearing. To ensure success, reared individuals should be biologically indistinct from those in the wild. We tested if this is true with monarch butterflies, Danaus plexippus , which are increasingly being reared for release by citizens and commercial breeders. Since late-summer monarchs should be as migration capable as possible for surviving the arduous long-distance migration, we evaluated four migration-relevant traits across two groups of captive-reared monarchs ( n = 41 and 42) and one group of wild-caught migrants ( n = 41). Monarchs (descendants of wild individuals) were reared from eggs to adulthood either in a warm indoor room next to a window, or in an incubator that mimicked late-summer conditions. Using an apparatus consisting of a perch mounted to an electronic force gauge, we assessed ‘grip strength' of all groups, then used image analysis to measure forewing size, pigmentation and elongation. In three of the four traits, reared monarchs underperformed compared to wild ones, even those reared under conditions that should have produced migration-ready individuals. The average strength of reared monarchs combined was 56% less than the wild group, even when accounting for size. Their orange wing colour was paler (an indicator of poor condition and flight ability) and their forewings were less elongated (elongation is associated with migration propensity) than wild monarchs. The reason(s) behind these effects is unknown but could stem from the frequent disturbance and/or handling of reared monarchs, or the fact that rearing removes the element of natural selection from all stages. Regardless, these results explain prior tagging studies that showed reared monarchs have lower migratory success compared to wild.

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The fall migration flyways of monarch butterflies in eastern North America revealed by citizen scientists

Journal of Insect Conservation ◽

10.1007/s10841-008-9169-y ◽

2008 ◽

Vol 13 (3) ◽

pp. 279-286 ◽

Cited By ~ 59

Author(s):

Elizabeth Howard ◽

Andrew K. Davis

Keyword(s):

North America ◽

Eastern North America ◽

Monarch Butterflies

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High-intensity flight feather molt and comparative molt ecology of warblers of eastern North America

The Auk ◽

10.1093/ornithology/ukaa072 ◽

2021 ◽

Vol 138 (1) ◽

Author(s):

Ronald L Mumme ◽

Robert S Mulvihill ◽

David Norman

Keyword(s):

North America ◽

Parental Care ◽

High Intensity ◽

Bird Species ◽

Late Summer ◽

Positive Association ◽

Eastern North America ◽

Surprising Result ◽

Flight Feather ◽

Feather Molt

Abstract Rapid high-intensity molt of flight feathers occurs in many bird species and can have several detrimental consequences, including reductions in flight capabilities, foraging performance, parental care, and plumage quality. Many migratory New World warblers (family Parulidae) are known to have intense remigial molt, and recent work has suggested that simultaneous replacement of the rectrices may be widespread in the family as well. However, the phylogenetic distribution of simultaneous rectrix molt, and high-intensity flight feather molt more generally, has not been systematically investigated in warblers. We addressed this issue by examining flight feather molt in 13 species, representing 7 different warbler genera, at Powdermill Avian Research Center in southwestern Pennsylvania, USA. All 13 species replaced their 12 rectrices simultaneously, with the onset of rectrix molt occurring in the early-middle stages of high-intensity primary molt. As expected, single-brooded early migrants molted earlier than double-brooded species whose nesting activities extend into late summer. However, our finding that late-molting species replaced their primaries more slowly and less intensively than early molting species was unexpected, as late-molting species are widely hypothesized to be under stronger migration-related time constraints. This surprising result appears to be at least partially explained by a positive association between the pace of molt and daylength; shorter late-summer days may mandate reduced daily food intake, lower molt intensity, and a slower pace of molt. In comparison to other passerines, flight feather molt in warblers of eastern North America is extraordinarily intense; at its peak, individuals are simultaneously replacing 50–67% of their 48 flight feathers (all 12 rectrices and 6–10 remiges on each wing) for 2–3 weeks or more. Because molt of this intensity is likely to present numerous challenges for flight, avoiding predators, foraging, and parental care, the period of flight feather molt for warblers constitutes a highly demanding phase of their annual cycle.

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