Dataset DOI: 10.5061/dryad.h1893201k

Description of the data and file structure

Captures and measurements of Sickle-winged Nightjar at Reserva Natural Rincón de Santa María and a few other sites in northeastern Argentina, 2012-2025. The code and files come in two parts: (1) Morphometry, which includes the R script Morphometry.R and the two files Eleothreptus_measurements.csv and Eleothreptus months.csv, including captures at Reserva Natural Rincón de Santa María and other sites. (2) Survival, which includes the R script CJS_survival.R and the two files Eleothreptus_adult_capture_histories.xlsx and Eleothreptus_juvenile_capture_histories.xlsx. You can run these two sections independently from one another, although they are based on the same raw data. The morphometric sexing results of Part 1 were incorporated manually into the datasets for Part 2.

Files and variables

File: Morphometry.R

Description: Code for morphometry analysis of Eleothreptus anomalus, including sex determination by logistic regression using Monte Carlo Cross Validation in a for loop. Author: Kristina Cockle.

File: Eleothreptus_measurements.csv

Description: Morphometric measurements of Eleothreptus anomalus for input to Morphometry.R code. NA indicates missing values. Nestor Fariña took measurements on 86% of captures; Luis Pagano took 8%; Kristina Cockle and seven other collaborators took the remaining 6%.

Variables

• ID_Final = aluminum leg band number (unique to each individual bird)
• Localidad = Locality (RNRSM = Reserva Natural Rincón de Santa María, Corrientes, Argentina; CSJ = Campo San Juan, Misiones, Argentina; PPSanAntonio = Parque Provincial San Antonio, Corrientes, Argentina; ResDonLuis = Reserva Don Luis, Corrientes, Argentina)
• codigo_salida = date (night) of capture (YYYY-MM-DD). For birds captured after midnight, codigo_salida is the date of the previous day, so that all birds captured in the same night have the same codigo_salida.
• Year = year of capture
• Sexo_plum = sex by plumage (M = male, H = Female, from the Spanish [hembra]). Birds were sexed primarily by Nestor Fariña and Luis Pagano based on plumage characteristics in the field. Juvenile birds could not be sexed by plumage, but we assigned their sex retroactively if they were recaptured in adult plumage.
• Sexado_Mol = sex by molecular sexing (M = male, H = Female, from the Spanish [hembra]). Molecular sexing was performed by Cecilia Kopuchian and Simón Kraemer on a subset of juveniles.
• Sexo_final = final sex (M = male, H = Female, from the Spanish [hembra]), as determined by plumage and/or molecular sexing.
• Edad_final = age (A = Adult, I = intermediate, J = Juvenile, Pichón = nestling or recent fledgling [from Spanish]). Birds were aged by plumage or in some cases based on previous captures. Intermediates are approximately 1-year old birds in plumage that is transitioning from Juvenile to Adult.
• Peso = weight in grams [from Spanish], measured with a spring balance (1 g).
• Ala = wing chord in mm [from Spanish], measured with a wing rule.
• Secundarias = length of secondary feathers in mm [from Spanish]. As described in Cockle et al. (in press, Ornithology): "Beginning in October 2018, we measured the length of the secondaries by extending the right wing, hooking the wing rule on the radius (leading edge of the wing), and measuring to the tip of the 4th secondary (Fig. S2). Although this measurement is not typical in ornithology, it gave us repeatable results within individual birds on different dates (Table S1)."
• Cola = tail length in mm [from Spanish]. Measured using a ruler.
• Tarso = tarsus length in mm to final leg scale before toes divide [from Spanish]. This was not the measurement we used in the paper, as it was inconsistent, but it is included here because the Morphometry.R code assesses its usefulness.
• Tarso_completo = complete tarsus length in mm to between toes [from Spanish]. From Cockle et al. (in press, Ornithology): "We used a caliper (0.1 mm) to measure the tarsus as follows: we rested the movable caliper jaw on the distal tibial epiphysis (bony protrusion posterior to the tibiotarsal joint), and the static jaw between the 2nd and 3rd toes, which we kept flexed toward the 1st toe (Fig. S2)."
• Largo_total = total length from tip of beak to tip of tail [from Spanish]. From Cockle et al. (in press, Ornithology: "Beginning in October 2021, we measured the total length of each individual (from the tip of the bill to the tip of the tail) by lying them on their back on a wing rule (1 mm) and holding the tip of the bill against the top of the ruler (Fig. S2)."

File: Eleothreptus_months.csv

Description: Captures by month of the year, to assess intra-annual variation. NA indicates missing values.

Variables

• ID_Final = aluminum leg band number (unique to each individual bird)
• Localidad = Locality (RNRSM = Reserva Natural Rincón de Santa María, Corrientes, Argentina; CSJ = Campo San Juan, Misiones, Argentina; PPSanAntonio = Parque Provincial San Antonio, Corrientes, Argentina; ResDonLuis = Reserva Don Luis, Corrientes, Argentina)
• Night = date (night) of capture (YYYY-MM-DD). [Same as codigo_salida in other datasets]. For birds captured after midnight, this is the date of the previous day, so that all birds captured in the same night have the same value in this column.
• Month = Month of capture (1 = January, 2 = February, ... 12 = December)
• Lek_season = Was the observation in the lekking season when males display (August to December)? (1 = yes, 0 = no)
• Year = Year of capture (YYYY)
• Sexo_final = final sex (M = male, H = Female, from the Spanish [hembra]), as determined by plumage and/or molecular sexing.
• Edad_final = age (A = Adult, I = intermediate, J = Juvenile, Pichón = nestling or recent fledgling [from Spanish]). Birds were aged by plumage or in some cases based on previous captures. Intermediates are approximately 1-year old birds in plumage that is transitioning from Juvenile to Adult.
• Peso = weight in grams [from Spanish], measured with a spring balance (1 g).

File: CJS_survival.R

Description: Code for Cormack-Jolly-Seber models to estimate capture probability and survival of Eleothreptus anomalus by sex and age, based on data from Reserva Natural Rincón de Santa María, Corrientes, Argentina. Author: Alejandro Pietrek.

File: Eleothreptus_adult_capture_histories.xlsx

Description: Captures of adult Eleothreptus anomalus to use as input for Cormack-Jolly-Seber models of capture probability and survival (by sex). NA indicates missing values.

Variables

• ID_Final = aluminum leg band number (unique to each individual bird)
• Codigo_salida = date (night) (YYYY-MM-DD). For birds captured after midnight, codigo_salida is the date of the previous day, so that all birds captured in the same night have the same codigo_salida.
• Sexo_final = final sex (M = male, H = Female, from the Spanish [hembra]), as determined by plumage and/or molecular sexing.
• Edad_final = age (A = Adult). Birds were aged by plumage or in some cases based on previous captures. Intermediate-plumaged birds (approximately 1 year old, transitioning from juvenile plumage to adult plumage) were included here as adults.

File: Eleothreptus_juvenile_capture_histories.xlsx

Description: Capture histories of juvenile Eleothreptus anomalus at Reserva Natural Rincón de Santa María, Corrientes, Argentina, for Cormack-Jolly-Seber models estimating capture probability and survival. NA indicates missing values.

Variables

• ID_Final = aluminum leg band number (unique to each individual bird)
• ch = capture history, a series of seventeen 0s and 1s indicating whether the bird was captured (1) or not (0) in each of seventeen 6-month periods, starting on 21 September 2016. We assigned a 1 if the individual was captured at least once in the 6-month period, and a 0 if it was not captured during the 6-month period.
• sex = sex of the captured bird (M = male, H = female [from the Spanish, hembra]. For this dataset, we assigned sex based on (1) recaptures of the same individual in adult plumage (easy to distinguish the sex of adult birds by plumage), (2) molecular sexing (performed by Cecilia Kopuchian and Simón Kraemer at CECOAL-CONICET), or (3) - last option - morphometry. When assigning sex by morphometry, we used the output of our Monte Carlo Cross Validation logistic regression models with length of secondaries as the predictor variable. This latter approach is described by Cockle et al. (in press): "We used the following criteria to classify 45 juvenile individuals as female, male, or unknown sex. If 75% or more of the model iterations produced predictions (probability of being female) above 0.8, we assigned the individual the sex "female". If 75% or more of the model iterations produced predictions below 0.2, we assigned the individual the sex "male". In all other cases, we assigned "unknown sex" and excluded the individual from the analysis of survival and probability of recapture."
• age = age of the bird (categorical) when first captured. Age was determined by plumage and time of year. Age classification was performed by Nestor Fariña and Olga Villalba in consultation with Kristina Cockle and Luis Pagano. under6 = less than 6 months old when first captured. 6to12 = 6 to 12 months old when first captured. 

Code/software

We have included two R scripts. The first script, Morphometry.R (by Kristina Cockle), uses as input the files Eleothreptus_measurements.csv and Eleothreptus_months.csv. This script summarizes the morphometric measurements, runs logistic regression models under a Monte Carlos Cross Validation approach, predicts sex from juvenile measurements, and produces the morphometric figures included in Cockle et al. (in press, Ornithology) and its supplementary material. The second script, CJS survival.R (by Alejandro Pietrek), takes as input the files Eleothreptus_adult_capture_histories.xlsx and Eleothreptus_juvenile_capture_histories.xlsx, models survival and recapture rate (Cormack-Jolly-Seber models) separately for adults and juveniles, and produces the survival and recapture-related figures in Cockle et al. (in press, Ornithology).