MOLECULAR SEXING AND ITS RELATIONSHIP WITH THE SEMI-CONCEALED YELLOW CORONAL PATCH OF THE WHITE-THROATED SPADEBILL PLATYRINCHUS MYSTACEUS CANCROMUS

· In sexually monomorphic species, sex iden?ﬁca?on by molecular techniques is an important alterna?ve. In this study, we employed molecular sexing to determine the sex of seven adult females, two immature females, one female with missing age data

In this study, the sex of the White-throated Spadebill Platyrinchus mystaceus cancromus Temminck, 1820 was determined, and its associa?on with age and the presence of a semi-concealed yellow coronal patch was evaluated.
The study was carried out at Brigida Farm (20°21'39"S; 43°30'39"W -250 ha), an experimental farm belonging to UFOP.The farm is in a transi?onalzone between the Cerrado and Atlan?c Forest domains.The vegeta?on is a semi-deciduous seasonal forest, riparian woodland, and rupestrian fields.Access to the farm is restricted with no logging or burning within its limits.The climate of the region is humid subtropical (Cwb according to the Köppen climate classifica?on), with dry winters and mild summers, an average annual temperature of 20°C, and an average annual rainfall of 1,250 mm (Alvares et al. 2013).
The White-throated Spadebill is a small Neotropical flycatcher (Tyrannidae) recognized by its broad, flat bill, mustache, and its solitary behavior.The species is insec?vorous and is found in a variety of habitats, including forest understory, riparian forests, and forest-edge bamboo thickets (del Hoyo et al. 2020).The breeding season of the species occurs during the rainy season, from October to December.It has been proposed (del Hoyo et al. 2020) that adult males have a semi-concealed yellow coronal patch (Figure 1), whose feathers can be erected in a notable fan, whereas in adult females, the coronal patch is small or absent.There are no reports of semi-concealed yellow coronal patch in juveniles so far (del Hoyo et al. 2020).
White-throated Spadebills were sampled between June 2018 and September 2019.Birds were captured using Ecotone mist-nets (18 x 3 m, five shelves and 19 mm mesh), opened at 06:00 a.m., checked every 30 min, and closed at 12:00 p.m.All captured birds were tagged with individual aluminum bands provided by CEMAVE/ICMBio (Permission 4385).The presence of a semi-concealed yellow coronal patch and the age of the birds were recorded.We assigned them as adults or juveniles, based on the yellowish labial commissure and the absence of a whi?sh spot at the base of the mandible, which is only seen in juveniles (Sick 1997, Macario et al. 2017).Blood samples were collected by puncturing the brachial vein with a sterile needle (13 x 4.5 mm).Blood was stored on filter paper (Unifil®) at -4°C un?l DNA extrac?on.
We captured 32 White-throated Spadebills and sexed them by PCR.PCR products were single-banded for males (ZZ) and double-banded for females (ZW).Bands were inconclusive for one bird; therefore, its sex was not determined (Figure 2, column 16).Of the successfully sexed birds, 10 were female and 21 were male (Figure 2).The sex of the 12 recaptured birds was confirmed on their second capture (individuals indicated by an asterisk in Figure 2).
A[er molecular sex determina?on,we examined the possible associa?on between sex and age, and the presence or absence of a semi-concealed yellow coronal patch.All 21 males were adults and exhibited a semi-concealed yellow coronal patch.Seven adult and one juvenile female exhibited patches.One female of uncertain age also exhibited a patch, and one juvenile female did not have a patch.
We conclude that the semi-concealed coronal of Whitethroated Spadebills is not an unequivocal sexually dimorphic trait.This finding supports previous observa?onsthat this trait is present in all males but also in some females (del Hoyo et al. 2020).However, our study also provides novel informa?on by recording the presence of a coronal patch in juvenile females.Regre)ably, the Brazilian field guides (Gwynne et al. 2010, Sigrist 2013, Ridgely et al. 2015) do not provide precise informa?on on the presence or absence of a semi-concealed yellow coronal patch in this species.Semi-concealed coronal patches are frequent among species of Tyrannidae (del Hoyo et al. 2020), and our results support that distribu?onacross sexes and immatures should not be overlooked in flycatchers.