BUSCADOR RECOLECTA

Quail eggs have been widely used in field experiments, mainly to study factors
associated with the risk of nest predation. Some shortcomings of using quail eggs in
this type of study have been previously addressed (e.g., these eggs might be too big for
some predators of eggs of small birds). Here, we show experimental evidence of
another shortcoming of the use of these eggs in field experiments. Quail eggs exposed
to sunlight rapidly faded in colour after three days, both in the visible and UV
spectra, and this change was related to the amount of solar radiation received. This
caused changes in the camouflage of the eggs, which may be perceived by predators
with different visual systems (dichromatic, trichromatic, and tetrachromatic (for
both violet- and UV-sensitive species)). Therefore, the results of field studies of
nest predation using quail eggs might be questioned in those cases in which the
camouflage has been altered due to the rapid changes in coloration, as this can affect
the resulting predation rates. We recommend that researchers planning to use quail
eggs should perform a prospective assessment of changes in coloration of eggs
exposed to environmental conditions in the nest sites used by the target species., This study was funded by grant CGL2017-83518-P from Ministerio de Economia, Industria y Competitividad, Spain, with EU-ERDF financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Quail eggs have been widely used in field experiments, mainly to study factors
associated with the risk of nest predation. Some shortcomings of using quail eggs in
this type of study have been previously addressed (e.g., these eggs might be too big for
some predators of eggs of small birds). Here, we show experimental evidence of
another shortcoming of the use of these eggs in field experiments. Quail eggs exposed
to sunlight rapidly faded in colour after three days, both in the visible and UV
spectra, and this change was related to the amount of solar radiation received. This
caused changes in the camouflage of the eggs, which may be perceived by predators
with different visual systems (dichromatic, trichromatic, and tetrachromatic (for
both violet- and UV-sensitive species)). Therefore, the results of field studies of
nest predation using quail eggs might be questioned in those cases in which the
camouflage has been altered due to the rapid changes in coloration, as this can affect
the resulting predation rates. We recommend that researchers planning to use quail
eggs should perform a prospective assessment of changes in coloration of eggs
exposed to environmental conditions in the nest sites used by the target species, Peer reviewed

[ES] El conjunto de datos está dividido en tres subcarpetas, dentro de las cuales los datos se encuentran agrupados por especies:

Eggs: Proporciona más de 900 imágenes en formato RAW en el rango visual del espectro visible de puestas completas sobre fondo negro, correspondientes a 14 especies distintas.

Nests: Proporciona más de 800 imágenes de nidos de 6 especies distintas, tomadas en su entorno desde 1 metro de distancia y a 70 cm de altura. En este segundo conjunto de imágenes, se incluyen imágenes de los nidos tanto en el rango visible como en ultravioleta cercano.

Incubating Behavior: Proporciona más de 950,000 imágenes en formato jpg correspondientes a secuencias de vigilancia del comportamiento de incubación de 5 especies distintas, junto con información de las condiciones ambientales.
[EN] The dataset is divided into three subfolders, within which the data is grouped by species:

Eggs: Provides over 900 images in RAW format within the visible spectrum of complete clutches on a black background, corresponding to 14 different species.

Nests: Provides over 800 images of nests from 6 different species, taken in their environment from 1 meter away and at a height of 70 cm. This set includes images of the nests in both the visible range and near-ultraviolet.

Incubating Behavior: Provides over 950,000 jpg images corresponding to surveillance sequences of incubation behavior from 5 different species, along with information on environmental conditions., [ES] Este conjunto de datos, generado en el marco del proyecto CAMNID: CGL2017-83518-P, Plan Nacional I+D+i, contiene información visual sobre huevos, nidos y comportamiento durante la incubación de diferentes especies de aves de litoral (shorebirds). Permite la realización de análisis de coloración y moteado, entre otros, para las especies en estudio. Asimismo, se proporcionan secuencias de imágenes de monitorización de diversos nidos de estas especies a lo largo de 3 horas (entre las 12:00 y las 15:00) junto con las condiciones ambientales durante la vigilancia. Esto permite la realización de estudios de los comportamientos de estas aves durante la incubación, abriendo la posibilidad de estudiar diversos mecanismos de mitigación de estrés térmico o las alternancias parentales macho/hembra durante la incubación en función de las condiciones ambientales, [EN] This dataset, generated within the framework of the CAMNID project: CGL2017-83518-P, Plan Nacional I+D+i, contains visual information on eggs, nests, and incubation behavior of various shorebird species. It enables color and spotting pattern analyses, among other studies, for the species included. Additionally, it provides image sequences monitoring various nests of these species over a 3-hour period (from 12:00 to 15:00) along with the environmental conditions during the surveillance. This allows for studies of the birds' behavior during incubation, opening the possibility to study mechanisms of thermal stress mitigation and male/female parental alternation during incubation based on environmental conditions., CAMNID PROJECT: Grant: CGL2017-83518-P, Plan Nacional I+D+i: EFECTOS DE LAS INVASIONES GEOLOGICAS DE ORIGEN ANTROPICO SOBRE LAS ESTRATEGIAS DE CAMUFLAJE DE NIDOS EN EL CHORLITEJO PATINEGRO CHARADRIUS ALEXANDRINUS, The dataset is comprissed of three folders. Eggs, Nests, and BehavioralMonitoring. ** Folder: Eggs: Photographs of shorebird eggs from a zenital view in raw format. - INFORMATION_TABLE.xlsx: Excel file with information about each picture in the Eggs folder subset. Image name can be used as unique identifier. - Folders corresponding to eggs of 14 different species. Species name corresponding to folder name. - Inside each folder, a single RAW format image file for each egg is provided ** Folder: Nests: Zenital pictures of shorebirds nests in natural environments both in the Vis and UV wavelength ranges. - INFORMATION_TABLE.xlsx: Excel file with information about each picture in the Nests folder subset. Image name can be used as unique identifier. - Folders corresponding to 6 different species. Species name corresponding to folder name. - Inside each folder, two images per nest are provided. One for the visible wavelength range ({ImageName}_VIS.ARW) and another one for the UV range ({ImageName}_UV.ARW) **Folder: BehavioralMonitoring: Pictures showing the incubating activity of shorebird species. Additionally, environmental conditions are also provided. - README.txt: Readme file providing the description of each folder in the dataset - Folders corresponding to 5 shorebirds species being monitored. - Inside each species folder: ---subfolder: DATE_OF_OBSERVATION: | |---subfolder: DATALOGGERCODE (DTXX (XX from 0 to 9)) | |____FRAME_XXX_STD.jpg: XXXth Picture taken under normal conditions | |____YYY_ACT.jpg: YYYth Picture corresponding to a special activitity condition | |____DATA_LOGGER.txt: csv file containing enviromental conditions during this experiment. Updated every 100s | |____DTXX.gpx: GPS position of this observation (gpx standard format) | |____DTXX_GPS.txt: GPS position for this observation in txt format (the gpx file is not always available), Peer reviewed

Solar radiation is an important driver of animal coloration, not only because of the
effects of coloration on body temperature but also because coloration may protect
from the deleterious effects of UV radiation. Indeed, dark coloration may protect
from UV, but may increase the risk of overheating. In addition, the effect of coloration
on thermoregulation should change with egg size, as smaller eggs have higher
surface-volume
ratios and greater convective coefficients than larger eggs, so that
small eggs can dissipate heat quickly. We tested whether the reflectance of eggshells,
egg spottiness, and egg size of the ground-nesting
Kentish plover Charadrius
alexandrinus is affected by maximum ambient temperature and solar radiation at
breeding sites. We measured reflectance, both in the UV and human visible spectrum,
spottiness, and egg size in photographs from a museum collection of plover
eggshells. Eggshells of lower reflectance (darker) were found at higher latitudes.
However, in southern localities where solar radiation is very high, eggshells are also
of dark coloration. Eggshell coloration had no significant relationship with ambient
temperature. Spotiness was site-specific.
Small eggs tended to be light-colored.
Thermal constraints may drive the observed spatial variation in eggshell coloration,
which may be lighter in lower latitudes to diminish the risk of overheating as a result
of higher levels of solar radiation. However, in southern localities with very high levels
of UV radiation, eggshells are of dark coloration likely to protect embryos from
more intense UV radiation. Egg size exhibited variation in relation to coloration, likely
through the effect of surface area-to-
volume
ratios on overheating and cooling rates
of eggs. Therefore, differential effects of solar radiation on functions of coloration
and size of eggshells may shape latitudinal variations in egg appearance in the Kentish
plover., Peer reviewed