Has the number of coastal birds counted in the Delta region of British Columbia changed over the last decade?
NatureCounts.ca have kindly provided a large dataset which contains records of counts made by volunteers at various locations. The locations relevant to Delta are shown in the map below.(I've left in my coding to help me when I go back and revise the document)
There are three classes of birds which are of interest: swans, geese, and ducks. Totals for the ten locations are indicated in the table below. Group 1 is swans, Group 2 is geese, and Group 3 is ducks. I have just added up the counts from each of the ten locations.
birds <- read.csv("C:/Users/Stephen/Dropbox/delta/bmde_req_bccws_1366041932071/birdsgrouped.csv")
attach(birds)
btable <- table(yearcollected, group)
btable
## group
## yearcollected 1 2 3
## 2000 1 4 51
## 2001 2 3 49
## 2002 2 3 51
## 2003 1 2 20
## 2004 1 3 38
## 2005 2 4 44
## 2006 1 4 44
## 2007 2 5 55
## 2008 1 5 45
## 2009 1 3 26
## 2010 1 2 26
## 2011 1 3 68
## 2012 0 5 68
The plot below shows the same data over time. The top line is for ducks, which show both the greatest quantity and the greatest variance. The overall trend for ducks is slightly upward, but this is based on only a decade of measurements.
library(ggplot2)
btdfrm <- as.data.frame(btable)
colnames(btdfrm) <- c("year", "class", "freq")
p <- ggplot(btdfrm, aes(year, freq, group = class)) + geom_line(size = 2, colour = "blue")
p + ggtitle("Coastal Bird Counts 2000-12") + ylab("Count") + xlab("Year")
The next step is to cross-validate the bird-count data and then to correlate the counts with changes in agricultural land use.