This study was carried out in the south-central part of the Municipality of Durango, in the state of Durango, Mexico between coordinates 23˚58'15.9" and 23˚57'26.3" latitude north and 104˚30'18.0" and 104˚34'11.4" longitude east. Climate is temperate with summer rains (Cw) [12] .

We collected 40 specimens of each species during fall-winter of 2013 and spring-summer 2014 (collecting permit No. SGPA/DGVS/12294/13), after procedures set by the North American Banding Council (2001).

We measured the following variables: body weight in grams, and bill length (culmen), tarsus length, and wing and tail length in mm. Weight was measured with a Radwag^® analytical balance model WPT1C/1 scale 0.01 g accuracy and tarsus and head lengths were measured with a Surtek^® dial caliper model 122202 with 0.01 mm accuracy, for wing and tail we used a Avinet^® 15 cm wing and tail ruler model WING15ECON.

In addition, we measured the distance from distal end of parietal to the premaxilla (head length), distance from the rostral end of the premaxilla to the tip of the bill (bill length) and distance from the nares to the tip of the bill (culmen length). Tarsus length was measured from the joint of the femur to the joint of the feet. Wing length was measured folded from the bend of the wing to the largest primary and tail length from the base to the tip of the largest rectrix [13] .

We used the following body condition indexes (BCI):

[14] (1)

[15] (2)

[16] (3)

We used SAS [17] for basic statistics (proc UNIVARIATE) and we compared variables for both species by season and sex (proc ANOVA) after [18] . We performed a posteriori Tukey’s test with a p > 0.05 for significance level.

We found that STRDEC was larger than ZENMAC for all the variables measured but tail length (Table 1). The

Same letter shows no statistical difference; Tukey’s test (p < 0.05); M: males; F: females.

body condition index did not show significant differences between seasons (Table 2) which may be related to substantial food availability during the whole year.

Previous studies have found these species to be generalists, studying ZENMAC [19] and STRDEC [20] . However, some other studies [21] [22] have found that STRDEC may consume some small invertebrates that contain protein of higher biological value.

Both species had a higher BCI during fall-winter, seasons coinciding with harvesting of some crops such as corn (Zea mays), and sorghum (Sorghum spp.), among others, suggesting that both species had access to resources of higher biological quality. In addition, migratory behavior of ZENMAC is benefited as doves can deposit more fat [23] resulting in higher weight.

Size and BCI of STRDEC was always higher than ZENMAC during both season, probably because of differences inherent to the species, which suggests that STRDEC may have a higher survival [8] .

The body condition index and morphometrics for male STRDEC were always higher than in females for both seasons (p = 0.05), as is well established by several authors [24] [25] . In addition some studies have found that physical condition and weight is related to androgen levels in males [26] . We also found significant differences in head (p = 0.002) and tail (p = 0.05) length between males and females, except for culmen length.

In ZENMAC, we found sexual dimorphism in weight, as found by [27] . However, we found a higher BCI in females compared to males (p = 0.021) during both seasons, suggesting that females are more able to get food resources or more properly, it may be related to egg production. Length measurements were higher in males than in females, in head (p = 0.006) and culmen (p = 0.026) length during fall-winter and wing (p = 0.01) and tail (p = 0.03) length during both seasons (Table 1).

Most morphometrics measurements (Table 3) and BCI showed significant differences (p < 0.001) but tail length (p = 0.124). STRDEC weight coincides with the reported in the Netherlands [24] (range 162.0 - 243.7 g) but it was lower than the one reported for some other sites in North America [25] (range 160.0 - 180.3 g).

Tail length of doves collected in Durango (10.4 - 14.9 cm) was higher than for other sites in North America (13.4 - 13.8 cm) but similar to those of the Netherlands (12.9 - 14.7 cm). Tarsus length also was higher in Durango (2.2 - 3.6 cm) than in other sites of both North America [25] and the Netherlands [24] . Body weight of ZENMAC (93.9 - 144.85 g) was closer to Marginella subspecies (86 - 142 g [27] ) than to Caroliniensis (100 - 170 [28] ).

STRDEC is a larger dove tan ZENMAC during both seasons, of course. Higher tolerance to human presence by STRDEC [29] compared to ZENMAC makes the species more abundant all year round as they have food

Body condition index: 1 [13] , 2 [14] , 3 [15] ; same letter shows no statistical difference; Tukey’s test (p < 0.05); M: male; F: females; SS: spring- summer season; FW: fall-winter season.

±: standard deviation of the morphometric variable.

resources provided by human populations [5] . Body size and its aggression towards other species [2] make STRDEC able to outcompete other dove species such as ZENMAC [30] .