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opencc-zeroOct 2021View details →

Digital biodiversity datasets reveal breeding phenology and its drivers in a widespread North American mammal

Shifts in reproductive timing are among the most commonly documented responses of organisms to global climate change. However, our knowledge of these responses is biased towards taxa that are easily observable and abundant in existing biodiversity data sets. Mammals are common subjects in reproductive biology, but mammalian phenology and its drivers in the wild remain poorly understood because many species are small, secretive, or labor-intensive to monitor. We took an informatics-based approach to reconstructing breeding phenology in the widespread North American deer mouse (Peromyscus maniculatus) using individual-level reproductive observations from digitized museum specimens and field censuses spanning >100 years and >45 degrees of latitude. We reconstructed female phenology in different regions and tested the importance of three environmental variables (photoperiod, temperature, precipitation) as breeding cues. Photoperiod and temperature were strong positive and negative breeding cues, respectively, while precipitation was not a significant predictor of breeding phenology. However, phenologies and the use of environmental cues varied substantially among regions, and we found evidence that these cueing repertoires are tuned to ecosystem-specific limiting conditions. Our results reiterate the importance of ecological context in optimizing reproduction and demonstrate how harmonization across biodiversity data resources allows new insight into phenology and its drivers in wild mammals.

opencc-zeroDec 2016View details →

Data from: Wintering areas predict age-related breeding phenology in a migratory passerine bird

Understanding connections between breeding, stopover and wintering grounds for long-distance migratory birds can provide important insight into factors influencing demography and the strength of carry-over effects among various periods of the annual cycle. Using previously described, multi-isotope (δ13C, δ15N, δ2H) feather isoscapes for Africa, we identified the most probable wintering areas for house martins (Delichon urbica) breeding at Badajoz in southwestern Spain. We identified two most-probable wintering areas differing in latitude in West Africa. We found that the probability to winter in the northern region was related to age and sex of individuals. Specifically, experienced males (i.e., two years or older) winter in the northern area with a greater probability than experienced females, whereas first-year females winter in the northern area with a greater probability than first-year males. In addition, wintering area was correlated with breeding phenology, with individuals wintering in the northern area initiating their clutches earlier than those wintering in the southern area. For birds wintering in the northern area, there was no relationship between age and clutch initiation date. In contrast, young birds wintering in the southern area initiated their clutches earlier than experienced birds wintering in this area. There was no significant correlation between wintering area and clutch size or the number of fledglings produced. We hypothesize that the relationship among social status, population density and winter habitat quality should be the most important driver of the carry-over effect we found for this population

opencc-zeroOct 2019View details →

Data from: 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 setting 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.

opencc-zeroDec 2019View details →

Data from: Plasma mammalian leptin analogue predicts reproductive phenology, but not reproductive output in a capital-income breeding seaduck

To invest in energetically demanding life history stages, individuals require a substantial amount of resources. Physiological traits, particularly those related to energetics, can be useful for examining variation in life history decisions and trade-offs because they result from individual responses to environmental variation. Leptin is a protein hormone found in mammals that is proportional to the amount of endogenous fat stores within an individual. Recently, researchers have confirmed that a mammalian leptin analogue (MLA), based on the mammalian sequence of leptin, is present with associated receptors and proteins in avian species, with an inhibitory effect on foraging and body mass gain at high circulating levels. While MLA has been both quantified and manipulated in avian species, little is currently known regarding whether plasma MLA in wild-living species and individuals is associated with key reproductive decisions. We quantified plasma MLA in wild, Arctic-nesting female common eiders (Somateria mollissima) at arrival on the breeding grounds and followed them to determine subsequent breeding propensity, and reproductive phenology, investment, and success. Common eiders are capital-income breeding birds that require the accumulation of substantial fat stores to initiate laying and successfully complete incubation. We found that females with lower plasma MLA initiated breeding earlier and in a shorter period of time. However, we found no links between plasma MLA levels and breeding propensity, clutch size or reproductive success. Although little is still known about plasma MLA, based on the current study and due to its role in influencing foraging behaviours and condition gain, it appears to be closely linked to reproductive timing and is therefore likely to underlie trade-offs surrounding life history decisions.

opencc-zeroDec 2021View details →

Population structure and dynamics, breeding activity and phenology of the blue-sided treefrog (Agalychnis annae)

Agalychnis annae is a species endemic to Costa Rica and Panama with populations shrinking or disappearing from several locations. We studied the reproduction of a relict population of A. annae in a 1,300 m2 natural pond in Costa Rica during 2007–2008. We marked adults with a visible implant alphanumeric tag injected in the thigh. We measured reproductive effort considering calling males per night and per hour, number of pairs in amplexus, and number of egg masses. We summed 366 individual observations: 57% juveniles, 39% adult males and 4% adult females. Average SVL was 29 mm (juveniles), 63 mm (males) and 78 mm (females). Sex ratio (males:females) was 4.85:1, while operational sex ratio varied between 1–6 males per female when both sexes were present at the pond. Maximum estimated census population size varied between 27 and 59 individuals, with a Ne = 43.11. Calling activity occurred mostly from 1800 h – 2000 h, and we counted 65 egg masses. Number of adults and calling males were positively correlated with accumulated rainfall and average temperature. Number of egg masses was positively correlated with the number of adults, accumulated rainfall, and average temperature. The causes of the long-term population decline must be identified to conserve A. annae and similar species, as well as establishing long-term monitoring programs. Required conservation actions include: translocation individuals from risky areas, creation of artificial ponds to increase ecological connectivity, elimination of introduced species, particularly in small habitat remnants, and establishment of ex situ conservation programs.

FIG. 4 in Staggered-Entry Analysis of Breeding Phenology and Occupancy Dynamics of Arizona Toads from Historically Occupied Habitats of New Mexico, USA

FIG. 4. Estimated detection probability from the simple multi-season model fitted with calling data from historical and control sites, based on the relationship between detection and Julian date from the simple multi-season occupancy model. Julian values represent only the values present in our data set and range from 1 March to 30 May (Julian days 60–150).

FIG. 3 in Staggered-Entry Analysis of Breeding Phenology and Occupancy Dynamics of Arizona Toads from Historically Occupied Habitats of New Mexico, USA

FIG. 3. Estimated probabilities of yearly occupancy (y-axis; 6 95% CI) from the historically occupied (orange) and control (blue) sites for the (A) staggered-entry model (SE) and the (B) simple multi-season (SMS) model. Dotted error bars represent years when surveys were not conducted.

FIG. 2 in Staggered-Entry Analysis of Breeding Phenology and Occupancy Dynamics of Arizona Toads from Historically Occupied Habitats of New Mexico, USA

FIG. 2. Estimated probabilities of Arizona Toads entering sites between subsequent surveys (orange), given that they have not previously entered, based on the estimated relationship between entry and Julian date. Estimated probabilities of Arizona Toad departing sites between subsequent surveys (blue), given that they are already present, based on the estimated relationship between departure and Julian date. Yellow points show the probabilities that toads were available to be detected for each day. Julian values range from 1 March to 30 May.

FIG. 1 in Staggered-Entry Analysis of Breeding Phenology and Occupancy Dynamics of Arizona Toads from Historically Occupied Habitats of New Mexico, USA

FIG. 1. Study area in southwestern New Mexico showing historically occupied (n ¼ 86; red circles) and control (n ¼ 59; blue triangles) waterbodies sampled during the 2013–2016 and 2019 breeding seasons for the Arizona Toads (Anaxyrus microscaphus). Filled shapes represent sites where we detected toads at least once, and open shapes represent sites where we never detected toads. Basemap by Stamen Design, under CC BY 3.0.

opencc-zeroDec 2017View details →

Data from: Impact of urbanization on abundance and phenology of caterpillars and consequences for breeding in an insectivorous bird

Urbanization can have marked effects on plant and animal populations' phenology, population size, predator-prey interactions and reproductive success. These aspects are rarely studied simultaneously in a single system, and some are rarely investigated, e.g. how insect phenology responds to urban development. Here, we study a tri-trophic system of trees – phytophagous insects (caterpillars) – insectivorous birds (great tits) to assess how urbanization influences i) the phenology of each component of this system, ii) insect abundance and iii) avian reproductive success. We use data from two urban and two forest sites in Hungary, central Europe, collected over four consecutive years. Despite a trend of earlier leaf emergence in urban sites there is no evidence for an earlier peak in caterpillar abundance. Thus, contrary to the frequently stated prediction in the literature, the earlier breeding of urban bird populations is not associated with an earlier peak in caterpillar availability. Despite this the seasonal dynamics of caterpillar biomass exhibited striking differences between habitat types with a single clear peak in forests, and several much smaller peaks in urban sites. Caterpillar biomass was higher in forests than urban areas across the entire sampling period, and between 8.5 and 24 times higher during the first brood's chick-rearing period. This higher biomass was not associated with taller trees in forest sites, or with tree species identity, and occurred despite most of our focal trees being native to the study area. Urban great tits laid smaller clutches, experienced more frequent nestling mortality from starvation, reared fewer offspring to fledging age, and their fledglings had lower body mass. Our study strongly indicates that food limitation is responsible for lower avian reproductive success in cities, which is driven by reduced availability of the preferred nestling diet, i.e. caterpillars, rather than phenological shifts in the timing of peak food availability.

opencc-zeroJun 2021View details →

Age-related breeding success in little penguins: A result of selection and ontogenetic changes in foraging and phenology

Reproductive performance typically improves with age, reaching a plateau at middle age and subsequently declining in older age classes (senescing individuals). Three potential non-exclusive mechanisms can explain the improvement in reproductive performance with age: (1) selection (poor quality individuals are removed from the population with increasing age), (2) constraint (individual efficiency increases through experience) and (3) restraint (reproductive investment increases with age as the residual reproductive value decreases). While all three mechanisms received strong empirical support, few studies have aimed at teasing apart those hypotheses and understanding their underlying functioning. In little penguins (Eudyptula minor), we used a 19-year longitudinal dataset on breeding and foraging of more than 450 individuals to investigate the effect of age on breeding success. We separated within- from among-individual age-effects using state-of-the-art statistical methods (within-subject centering and population change decomposition). We then assessed whether within-individual changes in breeding resulted from ontogenetic changes in foraging performances, breeding phenology or access to mates and nest sites. Fidelity and assortative pairing explained the high correlation in male and female ages within a pair. Breeding performances followed a typical bell-shaped curve with performance increasing up to 8 years-old, before reaching a plateau and subsequently declining after age 16. Both selection and within-individual processes occurred, although within-individual changes dominated differences in age-dependent breeding success. The selective appearance had almost no effect (apart from ages 2 to 3), and selective disappearance mostly affected changes at old ages (above 16), although they were also responsible for the slight increase in reproductive performances from ages 5 to 8. Focusing on within-individual changes, birds exhibited higher performances at middle ages, with birds foraging better, laying earlier and changing partner and nest less often. Their reproductive investment did not vary with age for females and slightly decreased for males. This supports the constraint hypothesis but not the restraint one. Finally, the increase in breeding performances at young ages was explained by the age-related increase in foraging performances during chick-rearing and advancement of laying. In contrast, reproductive senescence was defined by a general decrease in bird performances.

opencc-zeroDec 2017View details →

Data from: Phenological mismatch drives selection on elevation, but not on slope, of breeding time plasticity in a wild songbird

Phenotypic plasticity is an important mechanism for populations to respond to fluctuating environments, yet may be insufficient to adapt to a directionally changing environment. To study whether plasticity can evolve under current climate change, we quantified selection and genetic variation in both the elevation (RNE) and slope (RNS) of the breeding time reaction norm in a long-term (1973–2016) study population of great tits (Parus major). The optimal RNE (the caterpillar biomass peak date regressed against the temperature used as cue by great tits) changed over time, whereas the optimal RNS did not. Concordantly, we found strong directional selection on RNE, but not RNS, of egg-laying date in the second third of the study period; this selection subsequently waned, potentially due to increased between-year variability in optimal laying dates. We found individual and additive genetic variation in RNE but, contrary to previous studies on our population, not in RNS. The predicted and observed evolutionary change in RNE were, however, marginal, due to low heritability and the sex limitation of laying date. We conclude that adaptation to climate change can only occur via micro-evolution of RNE, but this will necessarily be slow and potentially hampered by increased variability in phenotypic optima.

opencc-zeroApr 2020View details →

Data from: Bioacoustic monitoring reveals details of tricolored blackbird breeding phenology

Bioacoustic monitoring has been used to study behaviors of organisms from insects to whales. Studies using multiple vocalizations of a single species have the potential to determine detailed phenology, but to date are rare. We tested whether bioacoustic monitoring of multiple gender- and age-specific vocalizations of the imperiled tricolored blackbird Agelaius tricolor could provide detailed information on reproductive phenology and breeding success. Using inexpensive cell phones and free software applications, we collected audio recordings of tricolored blackbird colonies during their breeding season. Adding solar panels enabled the stations to run autonomously, and use of cellular data enabled remote uploading of recordings. Analysis of the presence or absence of three vocalizations (male song, female song, and nestling call) provided a rich and detailed description of the breeding phenology, including the dates for courtship, onset of nest building, incubation, nestling hatching, and fledgling departure from nesting colonies. The resulting detail was more granular and accurate than comparable data from field monitoring, although field monitoring provides data such as abundance counts that bioacoustic monitoring does not. This information has a wide range of applications to research and conservation, from enabling more accurate abundance estimates, to assessing colony success or failure with fewer visits, to providing stronger guidance for when a colony must be protected from disruption.

publicSep 2016View details →

Data from: Breeding phenological response to spring weather conditions in common Finnish birds: resident species respond stronger than migratory species

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publicDec 2019View details →

Data from: Plasma mammalian leptin analogue predicts reproductive phenology, but not reproductive output in a capital-income breeding seaduck

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publicNov 2018View details →

Data from: Phenological mismatch drives selection on elevation, but not on slope, of breeding time plasticity in a wild songbird

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