Author: Rubega, Margaret

Lecture Notes: Respiration and circulation

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EEB 4260: Ornithology Respiration and circulation

Class Business:

We will review the FORMAT and PROCESS for the midterm exam today

Reading for this lecture
Required. Gill: Chapter 6, especially pages 141-150

Optional. Procter & Lynch: Pages 189-218

1. Respiration in birds

A) HIGHLY EFFICIENT

  1. i)  Respiration in birds differs significantly from that in mammals. In particular birds have a“one-way” system of airflow, which creates a continuous stream of air moving through the system (like a river). In contrast, in mammals air moves in and out (like the tide) along the same passages, causing air that is already in the system to impede the movement of incoming air.
  2. ii)  In birds, nearly all of the air in the lungs is replaced on each breath. This is not true in mammals. Consequently, birds are able to transfer more oxygen to their blood on each breath than are mammals.

iii) The tissue of bird lungs is much denser than that in mammals. Therefore, birds are able to accomplish much more with a smaller, more compact lung than a mammal could.

B) AIR SACS

  1. i)  A major peculiarity of the avian respiration system is the presence of air sacs. These arefound only in birds and help to create the one-way airflow that allows bird respiration to be so efficient.
  2. ii)  Air sacs are discrete, organized structures, that fill parts of a bird’s body cavity and extend into wing and leg bones.
  3. iii)  In addition to their role in respiration, air sacs help to remove excess heat from the body during flight and, when inflated, function as shock absorbers and protect internal organs. Male frigatebirds also use the air sacs in their neck in their breeding displays.

2. Circulation in birds

A) AVIAN HEARTS

  1. i)  Birds have 4-chambered hearts that are rather similar to those of mammals (and unlike the 3-chambered hearts of reptiles). One key difference is that the aortic arch arches to the right in birds and the left in mammals. In both mammals and birds there is a double- circulatory system, with one system of vessels taking blood to and from the lungs, and another transporting blood to and from the rest of the body.
  2. ii)  Compared to mammals, birds have relatively large hearts, high cardiac output, high heart rates (typically 150-350 beat per min when resting, higher when flying), and high blood pressure (up to 300-400 mm mercury).
  1. iii)  These features, combined with a very efficient respiration system, mean that they can get oxygen to their muscles rapidly and maintain the high metabolism needed to fly and live extremely active lives.
  2. iv)  But, these features – especially the resultant high blood pressure – also mean that birds have hearts that are prone to high failure rates and birds die of cardiac failure quite easily.

B) MODIFICATIONS TO THE CIRCULATION SYSTEM

  1. i)  Various types of birds have certain specializations in their circulatory systems.
  2. ii)  The ability to alter blood flow to the legs helps some birds thermoregulate, see Lecture 6, section 3B(v).
  3. iii)  Diving birds are capable of limiting blood flow to non-essential tissues, and thereby reduce oxygen consumption, while diving. This allows them to feed underwater without adverse effects.

Lecture Notes: Digestion, excretion and water balance

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EEB 4260: Ornithology

Digestion, excretion and water balance

 

Class Business

Reading for this lecture
Required. Gill: Chapter 6, pages 164-179

Optional. Procter & Lynch: Pages 175-188, 219-239

1. The digestive system

A) OVERVIEW

  1. i)  Digestion is the process by which food is turned into the fuel that birds use to grow, fly, stayalive, reproduce, etc. This process involves the following stages: maceration, digestion, assimilation, and excretion.
  2. ii)  The key parts of the digestive system that you will be expected to know the names and function of are: esophagus, crop, proventriculus, gizzard, small intestine, and ceca.
  3. iii)  Details of the digestive system vary considerably among birds depending on what they are eating.

B) MACERATION
i) A defining feature of digestion in birds is that birds do not have teeth with which to chew up

(macerate) their food.

ii) Maceration can be important because it breaks food up into small pieces which makes them easier to swallow and increases the rate of digestion (because the surface area over which digestion can occur is increased).

iii) Some birds macerate their prey externally. Raptors often rip large prey up into little pieces before swallowing them. Kingfishers beat their prey against a branch repeatedly to break up the bones. Some fruit eaters will crush berries with their bills prior to swallowing.

iv) Most birds macerate their prey internally, using the muscular portion of the stomach (the gizzard). Often birds will eat grit, which accumulates in the gizzard and presumably helps with grinding up the food.

C) DIGESTION

  1. i)  Birds tend to digest food very rapidly and food passes through their bodies at a high rate.
  2. ii)  Digestion begins in the proventriculus where gastric acids and digestive enzymes are produced. It then continues as the food passes through the gizzard and the small intestine.

iii) The length of the small intestine varies depending on the bird’s diet. Birds that eat poor quality food, or food that takes time to digest, tend to have longer small intestines than those that eat easily digested food. Increasing the length increases the amount of time it takes for food to pass through the system, maximizing the amount of nutrition that can be obtained. In birds that switch diets seasonally, intestine length can also change to accommodate diet shifts.

D) ASSIMILA TION

  1. i)  The uptake of nutrients occurs in the small intestine.
  2. ii)  Assimilation efficiency varies depending on the type of food (e.g., nectar is assimilated with great efficiency; old leaves and pine needles are not), the rate at which food passes through the gut (assimilation increase with higher passage rates), and with acclimation to a particular food type.

E) EXCRETION

  1. i)  Waste materials are excreted from the small intestine through the cloaca.
  2. ii)  In birds, nitrogenous wastes are excreted as uric acid. In contrast, mammals excrete urea. But, urea is toxic unless it is greatly diluted. Consequently, mammals need to drink a lot of water, while birds are able to store nitrogenous wastes at very high concentrations without using so much water. This water conservation gives birds advantages, especially in arid conditions. Uric acid also has big advantages for egg layers because it doesn’t need dilution and is insoluble in water. Consequently, much more nitrogenous waste can be stored in the small space within the egg than if it were in the form of urea.
  3. iii)  Salt glands are not a part of the digestive system, but they are involved in excreting waste products from the body. They are used to pump salts out of the blood and to help birds to maintain water balance. Not all birds have these glands (which lie just above the eyes); they are especially common in waterbirds that are associated with salt water. In some species, they allow birds to drink salt water without ill effects.

F) FOOD FLOW IS NOT NECESSARILY ONE WAY
i) Bringing food to young: gulls will regurgitate partially digested fish to feed to their young.

ii) Birds that feed on prey with hard indigestible parts (bones, fur, shells, exoskeletons) regurgitate the material that they cannot digest in the form of pellets.

iii) Some birds produce food for their young in parts of their digestive systems. Petrels produce fatty stomach oils in their proventriculus which they feed to their chicks (they can also projectile vomit these oils at unwary predators and seabird biologists …. they’re nasty!). Pigeons and doves produce a substance referred to as “crop milk”.

 

EEB 4260: Final Exam Questions

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Spring 2016

 

Using information about the Order ____________________________________________ as evidence, and for examples, answer these questions:

1. What is the significance of flight (or lack therof) in the species diversity, geographic distribution, and characteristic biology of this order of birds?

 

2. How does the characteristic biology of this order relate to/result in the reproductive behaviors most common to the order?

 

3. Describe one example of adaptive convergence in one (or a group of) trait(s) with birds from another order. Explain how you know it is convergence, and not shared ancestry.

Lecture Notes: Avian Classification and Taxonomy

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Class Business

The Twitter Handle Worksheet is now overdue! Make sure you fill it out, and bring it to class! The Course Guidelines Form is WAY overdue; if you haven’t handed it in, you aren’t earning points no matter what you do.

Reading for this lecture

Required. Gill: Chapter 1, and online at www.whfreeman.com/gill3e

1. Taxonomic organization

A) BASICS OF TAXONOMY – A taxonomy is an ordered (formal) system of classifying and naming organisms. A taxonomy is not necessarily a phylogeny (= a hypothesis about the pattern of evolution that produced the groups of organisms being named), but in practice in modern biology, all taxonomies are hypotheses about evolutionary history and relatedness.

i) Organisms are arranged in a hierarchical fashion with nested taxonomic levels. The basic levels are Kingdom, Phylum, Class, Order, Family, Genus, Species (in this hierarchy, organisms are increasingly closely related as you get closer to the species level. Are all individuals in a species equally closely related?) In addition, some taxonomists use intermediary levels, such as subfamilies, subgenera, superspecies, etc.

ii) In addition to their common names all birds also have scientific (“Latin”) names. These are given as a binomial, with the genus name first (and capitalized) and the species name second (not capitalized). E.g., the scientific name for Canada Goose is Branta canadensis. Subspecies names are given as a trinomial, with the third part identifying the subspecies. E.g., the subspecies of Canada Goose that occurs in the Aleutian islands (and which is endangered) is called Branta canadensis leucopareia. Why do we bother to do this?

 iii) Birds are classified in the Kingdom Animalia, the Phylum Chordata, and the Class Aves. Within the Aves, the first major subdivision splits the birds into two superorders, the Palaeognathae (ratites and tinamous) and the Neognathae (all other modern birds).

B) WHAT YOU SHOULD LEARN

i) There is variation in the ways that birds are grouped by different experts (there is also a lot that isconsistent across taxonomies) and taxonomies do differ – a taxonomy is a hypothesis! You should be aware that there is variation, and all taxonomies CHANGE over time.

ii) During this lecture, I will simply provide an overview of the groups of birds in the world above the level of Orders.

iii) Over the course of the semester I expect you to select an Order of birds to summarize the availableinformation on, according to the Ordinal Summary Guidelines posted on the class website. You will pick an Order from those named on the website of our textbook (whfreeman.com/Gill3e). Your job will be to summarize in an orderly and useful fashion the following information: the name of your group (both common and scientific); how both the name and membership of the group has differed over time and analysis (for example, the Superorder Paleognathae either contains 5 orders, including the Struthioniformes = Ostriches, or, according to some authorities a single order, the Struthioniformes, with 5 families, including the Struthionidae =Ostriches), approximately how many species are in the order, and major characteristics of each group (e.g., where found, what type of bird, major defining anatomical and/or behavioral characteristics).

2. Superorder Palaeognathae

A) FEATURES

i) The Palaeognathae consists of a relatively small number of species and includes all ratites, plus the tinamous.

ii) The group dates back a long way and it has been suggested that they have a lot of “primitive” traits; thisis misleading, since all living bird groups have been evolving for a long time, and it is not at all clear that Paleognathes are more like the ancestor of all birds than any other kind of bird.

iii) Members of this group all have a distinctive arrangement of bones in their palates, and this arrangement is not found in other birds. This is a key trait that unites the group.

iv) Most of the birds in this group (all of the ratites) are also flightless and have a number of anatomical features that are associated with flightlessness (e.g., reduced keel on the sternum, reduced wing bones). Tinamous can fly, but are very terrestrial.

v) In this group males provide parental care, and the mating systems are often relatively unusual (e.g., polygynandry/promiscuity).

vi) Exact details of taxonomy and relationships between subgroups are controversial, but the ratites are generally considered to be monophyletic, with tinamous their closest relatives (i.e., their “sister” group). (in which case the name ends is “-idea” instead of “-iformes”).

3. Superorder Neognathae

A) FEATURES

i) This group includes all other modern birds.

ii) The group is united, and distinguished from the paleognathous birds by a different arrangement of bones in the palate.

iii) The neognathous birds are subdivided into approximately 24 orders.

iv) Some authorities divide the Superorder into two “infraclasses”: the Galloanserae (containing theGalliformes and Anseriformes) and the Neoaves (all other modern orders).