Population Dynamics

The nature of populations
Understanding population dynamics can help us understand the conservation of species. Some populations are sedentary, some populations migrate, some populations have bottle-necking  and some populations are far too large and need to be managed for control of size. Populations vary, in sum.
Monitoring techniques
NAWMP page demonstrates that there are people hard at work to measure populations of waterfowl in North America for optimal harvest rates by using airplanes to obtain large scale counts of migrating waterfowl. And from harvest rates, we can also know the amount of deaths per species per year for species able to be hunted.
Age of first breeding

Element 1 describes various ages of first breeding for birds across the expanse of the waterfowl groups. A general trend was diving ducks and geese was about 2 years and dabbling ducks breed at about one year.
Nest success 
Different types of nest habitats can effect the success of individual nests. For example, if one nests close to water, they are at higher risk for flooding. If one nests with mammals, they are more at risk for predation. Also, food has a huge factor on if an animal will be successful or not. For example, the Barnacle Goose had a very small success rate (21%) when little vegetation was present, but when there was high vegetation they had a much higher success rate (84%).
Survival from hatching to flegding
Due to the large yolk sacs that the eggs of waterfowl contain, some of the birds can last many days without food because they have enough reserves to tie them over, so starvation isn't too much of an issue. Predation of ducklings and  gooslings is an issue for survival. Luckily for the Swans (Cygnus) they are able to defend their young quite well due to their large size.
Post-flegding survival
How successful a parent was can really be determined by post-fledging survival. However, finding the hard data behind this is extremely time consuming and expensive. So we usually just use the fact that a bird fledged to be an indicator of success since other indicators are difficult to quantify. 
 Mortality- Main causes of natural mortality are 1) Disease, 2) Predation, 3) Starvation (the number one cause). Man-made mortality counts for the majority of mortality of waterfowl.
Disease
During class discussion, a classmate discussed Cholera in waterfowl. She said in her paper it found that higher levels of phosphorous triggered this bacterial outbreak which would in turn lead to Cholera. What could managers do about this to prevent future issues of Cholera outbreaks?  
Man-induced mortality
During discussion, a classmate had a paper that talked about harvest of waterfowl. Our papers were very similar so we discussed a little further to try and clear up our understanding of harvesting and its effect on waterfowl populations. In her paper, they proposed that harvest could help decrease the density of waterfowl populations and therefore survivorship would actually increase because there is not so much density. Upon hearing that, I create a hypothesis of why that could be: since there is less competition two waterfowl of equal fitness do not have to compete for food when the entire food source is vital for one of the birds. Therefore if one of those animals dies, the other is able to survive. Starvation is the reason for the most natural causes of death. My paper stated that harvest was additive which follows Jess' paper.
Mortality in relation to age and sex
A very interesting example of mortality in relation to age and sex was the Mute Swan's deaths of overhead wire collisions. It was found that the majority of swans killed were 2 year old. Why? The reason proposed is these swans are more frequently distributing to find their territories and therefore are more likely to collide with these wires.


The control of numbers

Compensatory mortality versus additive mortality. I have struggled a lot with this concept because I am not sure which one is right. Some of the literature says that our current state of harvest and some say it is compensatory. What is compensatory and additive harvest, exactly? Compensatory harvest is basically saying that the waterfowl taken from the natural world is done in a way that does not add anymore deaths then would be naturally taken. Additive, however, basically says animals that harvest increases the amount of deaths that would be normal for the natural world. It was kind of what I was talking about in two sections up: man-induced mortality.




The Barnacle Geese populations are increasing; however, due to their still small population size (under 125,000) these geese are not hunted. The most important thing that was found in the population growth was having proportion of successful breeding pairs in the population. This means that when the population starts to do bad, the first thing we should focus on the proportion of successful breeding pairs in the population. This parameter was not density-dependent. Rather the proportion of successful breeding pairs depended on snow and ice as well as the presence of foxes.