CUSUM charts for the Koel Common name queries.

<p>Red dots indicate a deviation of the number of tweets, in particular the upper part of the chart points to an increase in tweets. UDB: Upper Decision Boundary; LDB: Lower Decision Boundary.</p

CUSUM charts for the Bogong moth queries.

<p>Red dots indicate a deviation of the number of tweets, in particular the upper part of the chart points to an increase in tweets. UDB: Upper Decision Boundary; LDB: Lower Decision Boundary.</p

Number of hits from 1 July 2013 to 2 July 2014 for different queries as outlined in Table 1.

<p>The relevant hits were counted after manual processing of the tweet content (where feasible). The signal-to-noise ratio (SNR) represents the ratio of the number of relevant tweets over the number of total hits for each query.</p

Examples of Twitter conversation on the Bogong moth (left) and the Koel (right).

<p>Left figure reprinted from Twitter under a CC BY license, with permission from Tim the Yowie Man, original copyright 2014. Right figure reprinted from Twitter under a CC BY license, with permission from Kym Druitt, original copyright 2015.</p

Validation of Koel Twitter data against historical monthly sightings.

<p>The Twitter data are represented as time series of the weekly counts, while the historical data are shown as monthly bars that are replicated for each migration season. The grey shaded area delimits the time period in which tweets couldn’t be reliably captured.</p

CUSUM charts for the Koel symptomatic queries.

<p>Red dots indicate a deviation of the number of tweets, in particular the upper part of the chart points to an increase in tweets. UDB: Upper Decision Boundary; LDB: Lower Decision Boundary.</p

Overview of the queries used in this study.

<p>Three types of queries are distinguished: (1) a taxonomic query using the taxonomic classification, (2) a common name query using the common name of the species, and (3) a symptomatic query that searches for tweets that indicate the presence of the species without mentioning either the taxonomic or common name.</p

Lag parameters used to fit AR models for the Twitter time series.

<p>Lag parameters used to fit AR models for the Twitter time series.</p

Validation of Bogong moth Twitter data against ground truth data collected in surveys.

<p>The Twitter data are represented as time series of the weekly counts, while the survey data are shown as bar charts. The grey shaded area delimits the time period in which tweets couldn’t be reliably captured.</p