Reproduction in the Eared Dove: An exception to the classic model of seasonal reproduction in birds?

Three different seasonally expressed opsins are present in the brain of the Eared Dove, an opportunist breeder

Birds living at high latitudes perceive the photoperiod through deep-brain photoreceptors (DBP) located in deep-brain neurons. During long photoperiods the information transmitted by these photoreceptors increases the activity of the hypothalamic-pituitary-gonadal (HPG) axis, leading to gonadal development. The presence of photopigments such as VA-Opsin, Opn4, Opn5 and Opn2 in brain areas implicated in reproductive behaviors has been firmly established in several avian species with seasonal breeding, whereas their existence in opportunistic breeding birds remains unconfirmed. The Eared Dove is an urban and peri-urban dove that breeds throughout the year. Males of this species do not exhibit the typical gonadal regression/recrudescence cycle, thus posing the question of what occurs upstream of the HPG axis. We addressed this issue by first studying the presence of diverse opsins located in DBP in the brains of Eared Dove males and whether these photopigments changed their expression throughout the year. We carried out an immunohistochemistry analysis on three different opsins: Opn2 (rhodopsin), Opn3 and Opn5. Our results demonstrate the discrete neuroanatomical distribution of these opsins in the brain of Eared Dove males and strongly indicate different seasonal expressions. In the anterior region of the hypothalamus, Opn2-positive cells were detected throughout the year. By contrast, Opn5 was found to be strongly and seasonally expressed during winter in the anterior and the hypothalamic region. Opn3 was also found to be significantly and seasonally expressed during winter in the hypothalamic region. We thus demonstrate for the first time that males of the Eared Dove, have three different deep-brain opsin-expressing photoreceptors with differential location/distribution in the anterior and hypothalamic region and differential seasonality. The persistence of Opn2 and the strong seasonal expression of nonvisual photopigments Opn3 and Opn5 in two areas of the avian brain, which are associated with reproduction, could be the primary distinction between seasonal and opportunistic breeders.

Annual molt period and seasonal color variation in the Eared Dove´s crown

Molting is an important process in which old and worn feathers are exchanged for new ones. Plumage color is determined by pigments such as carotenes, melanin and by the ultrastructure of the feather. The importance of plumage coloration has been widely studied in different groups of birds, generally at a particular time of the year. However, plumage coloration is not static and few studies have addressed the change in plumage color over time and its relationship to reproductive tasks. The Eared Dove (Zenaida auriculata, Des Murs, 1847) has a melanistic coloration with sexual dichromatism in different body regions. The Eared Dove´s crown is the most exposed body region during the bowing display. Our objective was therefore to accurately determine the molting period of the crown feathers and study the seasonal variation in their coloration in females and males. Our findings indicate a molting period of 6 months (January to June). The new feathers are undergoing changes in their coloration from July to December. During that period we apply an avian vision model then enabled us to reveal a seasonal variation in the coloration of the crown feathers in both sexes, as given by a change in the chromatic distances. The highest values in the chromatic distances towards the reproductive period are given by a change in the UV-violet component of the spectrum, indicating changes in the microstructure of the feather. This change in crown coloration towards the breeding season could be linked to reproductive behaviors.

The effect of short, long, natural, and intermittent short photoperiods on meat-type Japanese quails

The present study aimed to investigate the effects of short (8L:16D), long (23L:1D), natural, and intermittent short (8L(15 min L and 45 min D):16D) lighting programs from day 7 of age on the growth performance, carcass attributes, humoral immunity responses, and blood variables of growing Japanese quails through a 4-week production trial. Birds under the long lighting program were found to have 6.88, 6.24, and 5.55% more body weight compared to the natural, short, and intermittent lighting programs, respectively. Feed intake (FI), body weight gain (BWG), and feed conversion ratio (FCR) have increased in those birds exposed to long photoperiod (P < 0.01). The feed conversion ratio in those birds exposed to the intermittent short lighting program improved by 6.92% compared to the long lighting program. The application of long photoperiod increased the relative weight of heart (P = 0.027), and liver and ovaries (P < 0.01), while it decreased the relative weight of breast meat (P = 0.06). Humoral immunity system has boosted in the birds exposed to intermittent short lighting program (P < 0.01). Applying the long photoperiod increased alkaline phosphatase, cholesterol, and triglyceride levels (P < 0.01), while total protein and calcium concentrations were increased using intermittent short lighting program (P < 0.01). The lowest heterophil-to-lymphocyte ratio was observed in the birds raised under the intermittent short lighting program (P < 0.001). The current study revealed that in terms of improving feed conversion ratio, health, and welfare, the intermittent short lighting program (8L (intermittent):16D) could be more appropriate and beneficial for meat-type Japanese quails.