DOI: 10.5061/dryad.vdncjsxwv
title: Using morphometrics to sex adult and juvenile Soras (Porzana carolina)

description: Determining the sex and age of individuals can be an essential element of
 conservation management, wildlife monitoring, and demographic analysis.
 For many members of the family Rallidae, distinguishing between males and
 females is challenging, even when the bird is in the hand. The Sora
 (&lt;em&gt;Porzana carolina&lt;/em&gt;), a secretive rail
 that occupies freshwater wetlands throughout the United States and Canada,
 represents a species that is challenging to sex in the field. Morphometric
 measurements can help sex birds of an array of species, including rails.
 However, no comprehensive morphometric model has been fully validated for
 sexing Soras. We used DNA analysis to confirm the sex of Soras captured in
 the field and logistic regression models to determine which morphological
 features were the best predictors of sex. Measurements from 108 Soras (31
 hatch year females (HY-F), 29 hatch year males (HY-M), 22 after hatch year
 females (AHY-F), and 26 after hatch year males (AHY-M)) were used to
 create our logistic regression model. Color definition and connectivity of
 the auricular patch to eye or nape was used as an additional
 characteristic in adult birds. Our top-ranked model was further validated
 using a sample of 72 individuals exhibiting intermediate traits that would
 be particularly challenging to distinguish in the field. Our top
 performing model incorporated culmen length and tarsometatarsus length as
 the features most predictive of sex and had an overall accuracy of 85%. If
 higher accuracy is desired, an inconclusive band, which eliminates birds
 of low model score, i.e. scores indicative of inconclusive sex (below + or
 - 1.2), can be used. The accuracy of remaining birds (75% of sample) will
 be increased to 95%. Our model shows that simple measurements of culmen
 and tarsometatarsus is useful in discriminating the sex of a large
 percentage of live-caught Soras. This morphometric model will facilitate
 further demographic studies of this species and may be useful in designing
 morphometric studies of other species in the family Rallidae.
description: Data was collected at
 Maryland-National Capital Park and Planning Commission’s Patuxent River
 Park in Jug Bay wetlands. A morphometric model was created using machine
 learning algorithms and software including: JMP 14® software (SAS
 Institute, Inc., Cary, NC), Matlab 2019b (The MathWorks Inc., Natick, MA),
 and scikit-learn 0.23.2 (open-source python package). The preferred model
 as selected by Akaike Information Criterion (AIC), Schwartz Information
 Criterion (SIC), and cross validation.
description: Microsoft Excel (open-source alternative: Google Sheets), MP 14®
 software (SAS Institute, Inc., Cary, NC), Matlab 2019b (The MathWorks
 Inc., Natick, MA), and scikit-learn 0.23.2 (open-source python
 package).
description: # Using morphometrics to sex adult and juvenile Soras (Porzana carolina)
 Sora were live caught on the Patuxent River in 2018 and 2020. Measurements
 of their weight (g), fat score (0-5) , culmen (mm), tarsus (mm), and toe
 (mm) were taken along with a blood sample. The blood samples were sent to
 DDC Veterinary (DNA Technology Park, 1 DDC Way, Fairfield, OH 45014) where
 a DNA blood test based on two conserved chromo-helicase-DNA (CHD) genes
 located on the avian sex chromosomes was used to determine the sex of each
 individual. Measurements from 108 Soras (31 hatch year females (HY-F), 29
 hatch year males (HY-M), 22 after hatch year females (AHY-F), and 26 after
 hatch year males (AHY-M) captured in 2018 were used to create our logistic
 regression model in Matlab. Our top-ranked model was further validated
 using a sample of 72 individuals captured in 2020 exhibiting intermediate
 traits that would be particularly challenging to distinguish in the field.
 Our top performing model incorporated culmen length and tarsometatarsus
 length as the features most predictive of sex and had an overall accuracy
 of 85%. If higher accuracy is desired, an inconclusive band, which
 eliminates birds of low model score, i.e., scores indicative of
 inconclusive sex (below + or - 1.2), can be used. The accuracy of
 remaining birds (75% of sample) will be increased to 95%. ## Description
 of the data and file structure Our raw data Microsoft Excel file shows the
 results of the DNA sexing done on live-caught Sora by DDC Veterinary (DNA
 Technology Park, 1 DDC Way, Fairfield, OH 45014) from 2018 and 2020. For
 each individual, it shows the year they were caught, the USGS band number,
 the researcher’s guess at the sex, the actual sex determined by DNA
 sexing, hatch year status, weight (g), fat score (0-5), and culmen (mm),
 tarsus (mm), and toe (mm) measurements. The raw data file sora_data.xlsx
 has the following columns: * CaptureYear: capture year for the sora *
 Band: band number of the captured sora * OurGuess: sex identification
 determined by our banding researchers * ACTUALSEX: sex determination from
 DNA testing * Y: main response variable coded as actualsex male: = Y = 1
 and actualsex female: = Y = 0 * Age: age group AHY = after hatchling year
 and HY = hatchling year * Age01: numerical coding of age with AHY coded as
 0 and HY coded as 1 * Cul: Culmen length in mm * Tar: Tarsometatarsus
 length in mm * Toe: middle toe length in mm * Wt: mass in grams * Fat: not
 used, but on a scale of 0-5 (0 being no visible fat to 5 being large
 amounts of visible fat) ## Data was derived from the following sources:
 Data are from DNA sexing done on live-caught Sora by DDC Veterinary (DNA
 Technology Park, 1 DDC Way, Fairfield, OH 45014) paired with measurement
 data taken by researchers at Maryland-National Capital Park and Planning
 Commission’s Patuxent River Park. ## Code/Software Matlab versions 2019b,
 2022b, and 2023a were the primary software tools used in the analysis
 Scripts assume that all scripts and supporting functions reside in the
 same folder. It is also assumed that the sora_data.xlsx data file resides
 in the same folder as the scripts.