In RS-eco/traitdata: Easy access to various ecological trait data

knitr::opts_chunk$set(collapse = TRUE, comment = "#>")

Morphological indices

Morphological indices can be helpful to depict ecological differences between feeding guilds and between species differing in their preferred foraging stratum.

There are 6 morphological indices, which are often calculated:

Kipp’s index (Kipp’s distance divided by wing length),
tail-wing index (the longest rectrix divided by wing length),
bill height index (bill height divided by bill length),
bill width index (bill width divided by bill length),
lateral tarsus index (lateral tarsus diameter divided by tarsus length) and
sagittal tarsus index (sagittal tarsus diameter divided by tarsus length).

Here, we show how to calculate these indices, using the data included in this package:

#' First we load our Data
library(traitdata)
data(passerines)

#' Secondly, we need to load the dplyr library
library(dplyr)

#' Now, we can calculate the indices using the mutate function from the dplyr package
passerines <- passerines %>% 
  mutate(tail_wing_index = Tail / Wing, 
         bill_height_index = `Bill D` / `Bill L`, 
         bill_width_index =  `Bill W` / `Bill L`)
#kipp_index = kipp / Wing,
#lateral_tarsus_index = lateral.tarsus.diameter / tarsus.length
#sagittal_tarsus_index = sagittal.tarsus.diamter / tarsus.length

Now, we want to plot these indices:

#' Load the ggplot2 library
library(ggplot2); library(patchwork)

#' Plot a histogram of the 3 indices
p1 <- passerines %>% ggplot() + geom_histogram(aes(x=tail_wing_index)) +
  scale_y_continuous(expand=expansion(add=c(0,10))) + 
  labs(x="Tail wing index", y="Frequency") + theme_bw()
p2 <- passerines %>% ggplot() + geom_histogram(aes(x=bill_height_index)) +
  scale_y_continuous(expand=expansion(add=c(0,10))) + 
  labs(x="Bill height index", y="") + theme_bw()
p3 <- passerines %>% ggplot() + geom_histogram(aes(x=bill_width_index)) +
  scale_y_continuous(expand=expansion(add=c(0,10))) + 
  labs(x="Bill width index", y="") + theme_bw()
p1 + p2 + p3