Megascops watsonii (Cassin, 1848)

Dantas, Sidnei M., Weckstein, Jason D., Bates, John, Oliveira, Joiciane N., Catanach, Therese A. & Aleixo, Alexandre, 2021, Multi-character taxonomic review, systematics, and biogeography of the Blackcapped / Tawny-bellied Screech Owl (Megascops atricapilla-M. watsonii) complex (Aves: Strigidae), Zootaxa 4949 (3), pp. 401-444 : 427-428

Megascops watsonii (Cassin, 1848)

Guianan Screech-Owl

corujinha-das-guianas (Portuguese)

Ephialtes watsonii Cassin, 1848 (lectotypes at ANSP examined)

Otus watsonii (Cassin, 1848) : Cory (1918; part: specimens east of the Negro and Amazon rivers including southern Venezuela, northern Brazil, Guiana, Surinam, and French Guiana).

Otus watsonii watsonii (Cassin, 1848) : Chapman (1928); Peters (1940); Marks et al. (1999); Weick (2006): 84 (part: specimens east of the Negro and Amazon rivers including southern Venezuela, northern Brazil, Guiana, Surinam, and French Guiana).

Megascops watsonii (Cassin, 1848) : König et al. (1999); König & Weick (2008; part: specimens east of the Negro and Amazon rivers including southern Venezuela, northern Brazil, Guiana, Surinam, and French Guiana).

Megascops watsonii watsonii (Cassin, 1848) : Dickinson & Remsen (2013); Clements et al. (2019); Gill et al. (2020) (part: specimens east of the Negro and Amazon rivers including southern Venezuela, northern Brazil, Guiana, Surinam, and French Guiana).

The type locality of this taxon is defined as “Orinoco River, Venezuela ” ( Chapman 1928) and it corresponds to Clade A recovered herein as the lineage of the Megascops atricapilla-M. watsonii complex restricted to the Guiana Shield, east of the Branco and Negro rivers, in Brazil, through Venezuela, Guyana, French Guiana, and Surinam. As reported above, sequences obtained from one of the lectotypes of M. watsonii (ANSP 2445) confidently placed it within Clade A ( Fig. 5 ). Statistical support for the reciprocal monophyly and significant coalescence of M. watsonii with respect to the other species in the complex was high in all analyses ( Figs. 3 and 4 ). Average corrected pairwise p-distances between M. watsonii and the remaining species in the Megascops atricapilla-M. watsonii complex were as follows: 6.7% ( M. usta ); 6.4 % ( M. stangiae ); 6.7% ( M. ater ); 6.6 % ( M. alagoensis ); and 7.1% ( M. atricapilla ).

Dark morphs of this species tend to be darker than individuals from other species in the Megascops atricapilla-M. watsonii complex, except for M. ater (see below), from which it differs mainly in back color. In some individuals of M. watsonii (e. g. MPEG 66635), the back is black. The darker individuals also tend to have wider and bolder underparts striping than in other species of the complex, which distinguishes them from M. ater dark morphs. However, as is usual within this genus, the tremendous individual variation in M. watsonii makes any generalization about diagnostic morphological characters impossible.

Longsong distinguishable from slower-paced longsongs of M. stangiae and M. usta and faster paced longsongs of M. atricapilla ( Fig. 9 : Tables 6 and 10 ). Shortsong faster-paced than in M. usta and M. stangiae ( Table 8 ).

Figures

FIGURE 3. Results of ML and BI phylogenetic analyses based on 3969 bp of the concatenated mitochondrial and nuclear genes sequenced in this study. Numbers associated with nodes represent BI posterior probability and ML bootstrap values respectively. Asterisks (*) represent BI values> 0.95 and ML values> 95%. Main clades (labelled A‒F) recovered by the molecular analyses are shown, along with the different areas of endemism where they occur, as follows: Gu (Guiana); Gu* (westernmost part of the Guiana area of endemism); Na (Napo); Im (Imeri); In (Inambari); Ro (Rondonia); Ta (Tapajós); Ta* (southernmost part of the Tapajós area of endemism); Xi (Xingu); Xi* (southernmost part of the Xingu area of endemism); Be (Belém); PE (Pernambuco); and AF (Atlantic Forest south of the Sao Francisco River). See also Fig. 1.

FIGURE 4. Species tree (ST) and BPP chronogram for the diversification of the Megascops atricapilla-M. watsonii complex. Main clades (labelled A‒F) recovered by the molecular analyses are shown. Black bars associated with each node are 95% credibility intervals for node ages (in mya). Numbers above black bars denote nodal posterior probabilities and signs below the bars are speciation probabilities under the three prior distributions used for BPP analysis. Asterisks (*) indicate high speciation probabilities (PP> 0.95).

FIGURE 5. ML results for the position of the Megascops watsonii lectotype (ANSP 2445) with respect to the Megascops atricapilla-M. watsonii clades recovered in the study.

FIGURE 9. Geographic variation in longsong paces (notes/s) across clades A–F in the Megascops atricapilla-M. watsonii complex. Locality codes are given as letters followed by numbers and can be found in full in the Appendix. Numbers next to locality dots represent locally measured longsong pace values. When more than one individual was sampled at a given locality, the total number of longsongs measured is given in parentheses, with reported values representing averages.