Bird SexChapter 14

Part 5 – Avian Life Histories

Gonadsgenitalia typically internal

• Paired testes in males

• 1 ovary in females (left side)– 2 ovaries typical of many raptors– 500 to several thousand primary oocytes

• Testes & follicles dramatic size changes– Affected by FSH & LH

• Follicle Stimulating Hormone & Luteinizing Hormone

• Produce testosterone & estrogen

Sex Chromosomes

• Females = heterogametes (ZW)– Inactive W sex chromosome– Active Z sex chromosome

• Males = ZZ

• Female’s ova determines sex of young

• Female’s seem to be able to adjust sex ratios in clutch!

Figure 1. The sex ratio in relation to hatching order in populations in (A) Montana (B) Alabama  

Sperm Production

• At night when cooler

• Stored at distal end of vas deferens; ~4° C cooler than body

Ova Maturation• Oocytes present at hatching

• Ova by 2 months of age

• Add yolk in week prior to ovulation– Time varies by spp. (4 to 16 days)

This female House Sparrow (Passer domesticus or HOSP ) was caught on March 23, 2008, and dissected. (HOSP are not protected under the federal Migratory Bird Treaty Act, as they are a non-native, invasive species.) This female had already laid four eggs in a nestbox. You can see the fifth egg in the oviduct, forming a lining over the egg yolkd and egg white. A sixth and seventh egg are forming with a yolk in the center of the photo. To the left are another 15 or so smaller "seed" eggs. The female HOSP can cut off this string when she completes a full clutch (HOSP generally lay 1-8 eggs per clutch.)

Fertilization

• Occurs at infundibulum– After cloacal kiss

– No phallus in most– Sperm swim to top in <30 min– Viable for 1-2 weeks

• Record = 72 d in chicken

(A) Harlequin Duck  & (B) African Goose, 2 species with a short phallus and no forced copulations, in which females have simple vaginas.

(C) Long-tailed Duck & (D) Mallard, 2 species with a long phallus and high levels of forced copulations, in which females have very elaborate vaginas (size bars = 2 cm).

] = Phallus, * = Testis, open star = Muscular base of the male phallus, > = upper and lower limits of the vagina

Development of Embryo

• Moves thru oviduct in ~24 hours:

– Albumen (3-4 hrs)

– Egg membranes (1 hr)

– Shell (20 hrs)

• Albumen – Magnum

• Membranes – Isthmus

• Shell – Uterus– Egg colors

Egg Composition

• Yolk = food supply – 21-36% lipids– 16-22% proteins

• Albumen = H20 supply– 90% H20

– 10% protein – Shock absorber (T & jarring)

• Shell– Protection (CaCO3)

– Thousands of pores = gas exchange

Egg Laying

• ~1 egg per day in most

• Vary in:– Shape– Size– Color– Number (lots of interest)

• Determinate Layers – lay a fixed #

• Indeterminate Layers – try for set # in nest

Exams

• Song portion of lab final on this Thursday

• Lecture Exam #3 – Monday - April 30– 8 a.m. in this room