/// <summary>
        /// Get bird nest activities from web service.
        /// </summary>
        private static void LoadBirdNestActivities()
        {
            BirdNestActivityList birdNestActivities;

            if (BirdNestActivities.IsNull())
            {
                // Get data from web service.
                birdNestActivities = new BirdNestActivityList();
                foreach (WebBirdNestActivity webBirdNestActivity in WebServiceClient.GetBirdNestActivities())
                {
                    birdNestActivities.Add(new BirdNestActivity(webBirdNestActivity.Id,
                                                                webBirdNestActivity.Name));
                }

                BirdNestActivities = birdNestActivities;
            }
        }